The G.O.P. claimed the momentum in the spring. Then the overturning of Roe v. Wade galvanized Democrats. As the momentum shifts again, the final stretch of the 2022 midterms defies predictability.Exactly one month until Election Day, Republicans remain favored to take over the House in November, but momentum in the pitched battle for the Senate has seesawed back and forth as a multimillion-dollar avalanche of advertising has blanketed the top battleground states.For almost two decades, midterm elections have been a succession of partisan waves: for Democrats in 2006, Republicans in 2010 and 2014, and Democrats again in 2018. Yet as the first mail-in ballots go out to voters, the outcome of the 2022 midterms on Nov. 8 appears unusually unpredictable — a reason for optimism for Democrats, given how severely the party that holds the White House has been punished in recent years.Three states in particular — Georgia, Nevada and Pennsylvania — that are seen as the likeliest to change party hands have emerged as the epicenter of the Senate fight with an increasing volume of acrimony and advertising. In many ways, the two parties have been talking almost entirely past each other both on the campaign trail and on the airwaves — disagreeing less over particular policies than debating entirely different lists of challenges and threats facing the nation.Republicans have pounded voters with messages about the lackluster economy, frightening crime, rising inflation and an unpopular President Biden. Democrats have countered by warning about the stripping away of abortion rights and the specter of Donald J. Trump’s allies returning to power. Both parties are tailoring their messages to reach suburban voters, especially women, who are seen as the most prized and persuadable bloc in a polarized electorate.Democrats have warned that Republican gains in the midterms would usher in the return of Donald J. Trump’s movement to power. Brittany Greeson for The New York TimesThe year has progressed like a political roller coaster. Republicans boasted that a typical wave was building in the spring, and Democrats then claimed the momentum after the Supreme Court’s decision overturning Roe v. Wade galvanized progressive and independent voters. Now the pendulum seems to have swung back.“I wish the election was a month ago,” conceded Navin Nayak, a Democratic strategist and the president of the Center for American Progress Action Fund. He was heartened, however, to see his party with a fighter’s chance, adding that Democrats had “no business being in this election.”The challenge for Democrats is that they also have no margin for error. Clinging to a 50-50 Senate and a single-digit House majority, they are seeking to defy not only history but Mr. Biden’s unpopularity. “Even the slightest tremor is going to put the Democrats in the minority,” as Peter Hart, a longtime Democratic pollster, put it.Come November, whichever party’s issue set is more dominant in the minds of the electorate is expected to have the upper hand.“The Democrats’ message is, ‘Elect Republicans and the sky may fall!’” Paul Shumaker, a veteran Republican strategist based in North Carolina, said, referring to rhetoric around abortion and Trumpism. But he said that voters “see the sky is falling — all because of Joe Biden’s bad economy. The increase in prices at the grocery store is an everyday fact of life.”The State of the 2022 Midterm ElectionsWith the primaries over, both parties are shifting their focus to the general election on Nov. 8.Standing by Herschel Walker: After a report that the G.O.P. Senate candidate in Georgia paid for a girlfriend’s abortion in 2009, Republicans rallied behind him, fearing that a break with the former football star could hurt the party’s chances to take the Senate.Wisconsin Senate Race: Mandela Barnes, the Democratic candidate, is wobbling in his contest against Senator Ron Johnson, the Republican incumbent, as an onslaught of G.O.P. attack ads takes a toll.G.O.P. Senate Gains: After signs emerged that Republicans were making gains in the race for the Senate, the polling shift is now clear, writes Nate Cohn, The Times’s chief political analyst.Democrats’ Closing Argument: Buoyed by polls that show the end of Roe v. Wade has moved independent voters their way, vulnerable House Democrats have reoriented their campaigns around abortion rights in the final weeks before the election.Republicans are bullish on taking the House. Representative Elise Stefanik of New York, the chair of the House Republican Conference, predicted a “red tsunami” in an interview. “I think we can win over 35 seats, which would give us the largest majority since the Great Depression,” she said.Republicans, in fact, need only a red ripple to take the gavel from Speaker Nancy Pelosi’s current threadbare 220-member majority. For Democrats to maintain power, they would need a near sweep of the battleground districts, winning roughly 80 percent of them, according to political analysts who rate the competitiveness of races.Dan Conston, who heads the Congressional Leadership Fund, the super PAC aligned with the House Republican leadership, noted that if Republicans win every seat that Mr. Trump carried, plus every seat that Mr. Biden won by five percentage points or less, they would secure 224 seats, a narrow six-seat majority.“The political environment has moved in multiple ways this cycle and has more contrasting issues that are keeping both sides engaged and energized,” Mr. Conston said.Republicans have improved their standing in several key Senate races, including one in Wisconsin, where Lt. Gov. Mandela Barnes, the Democratic candidate, has struggled recently.Haiyun Jiang/The New York TimesIt is Republican super PAC spending that has frightened House Democrats most in recent weeks.“We always knew this would be tough,” Representative Sean Patrick Maloney of New York, chairman of the Democratic Congressional Campaign Committee, said in an interview. Of the super PAC cash deficit, he said, “We just need enough.”In the Senate, the battlefield has been shaped by powerful crosscurrents and has swelled to as many as 10 states — and if a single state flips to the Republicans, they would control the chamber.Republicans have improved their standing in several key Senate races — including those in Nevada, Pennsylvania and Wisconsin — by pummeling Democrats over crime. But those gains have been offset in part by the struggles of several Republican nominees, including those in Arizona and in Georgia, where Herschel Walker’s campaign has been engulfed by the allegation that he financed an abortion for a former girlfriend.At a campaign stop in Wadley, Ga., Herschel Walker, the Republican Senate candidate, dismissed a report that he had paid for an ex-girlfriend’s abortion.Nicole Buchanan for The New York TimesOne of the most significant Senate developments came in New Hampshire, where Republicans nominated Don Bolduc in September despite warnings in Republican-funded television ads that his “crazy ideas” would make him unelectable. In a recent radio interview, Senator Rick Scott, the chairman of the National Republican Senatorial Committee, pointedly did not include New Hampshire among his party’s top five pickup opportunities. And late Friday, Mr. Scott’s group began canceling more than $5 million it had reserved there, saying it was redirecting the funds elsewhere.Recruiting failures have hampered Senate Republicans throughout 2022, and Senator Mitch McConnell, the minority leader, complained over the summer about “candidate quality.”.css-1v2n82w{max-width:600px;width:calc(100% – 40px);margin-top:20px;margin-bottom:25px;height:auto;margin-left:auto;margin-right:auto;font-family:nyt-franklin;color:var(–color-content-secondary,#363636);}@media only screen and (max-width:480px){.css-1v2n82w{margin-left:20px;margin-right:20px;}}@media only screen and (min-width:1024px){.css-1v2n82w{width:600px;}}.css-161d8zr{width:40px;margin-bottom:18px;text-align:left;margin-left:0;color:var(–color-content-primary,#121212);border:1px solid var(–color-content-primary,#121212);}@media only screen and (max-width:480px){.css-161d8zr{width:30px;margin-bottom:15px;}}.css-tjtq43{line-height:25px;}@media only screen and (max-width:480px){.css-tjtq43{line-height:24px;}}.css-x1k33h{font-family:nyt-cheltenham;font-size:19px;font-weight:700;line-height:25px;}.css-ok2gjs{font-size:17px;font-weight:300;line-height:25px;}.css-ok2gjs a{font-weight:500;color:var(–color-content-secondary,#363636);}.css-1c013uz{margin-top:18px;margin-bottom:22px;}@media only screen and (max-width:480px){.css-1c013uz{font-size:14px;margin-top:15px;margin-bottom:20px;}}.css-1c013uz a{color:var(–color-signal-editorial,#326891);-webkit-text-decoration:underline;text-decoration:underline;font-weight:500;font-size:16px;}@media only screen and (max-width:480px){.css-1c013uz a{font-size:13px;}}.css-1c013uz a:hover{-webkit-text-decoration:none;text-decoration:none;}How Times reporters cover politics. We rely on our journalists to be independent observers. So while Times staff members may vote, they are not allowed to endorse or campaign for candidates or political causes. This includes participating in marches or rallies in support of a movement or giving money to, or raising money for, any political candidate or election cause.Learn more about our process.But most Senate strategists now see control of the chamber hinging particularly on Nevada and Georgia, where Democratic incumbents are seeking re-election, and Pennsylvania, an open seat held by a retiring Republican. And whichever party wins two of those three would be strongly favored to be in the majority.Both sides are still seeking to stretch the map. A Democratic super PAC just injected more money into North Carolina, and Republicans have talked up their chances in Colorado. Millions of dollars are funding ads focusing on Republican-held seats in Ohio and Florida, as well.“This is the strangest midterm I’ve ever been a part of, because you have these two things in direct conflict,” said Guy Cecil, a veteran campaign operative who chairs the Democratic group Priorities USA. “You have what history tells us, and you have all this data that says it’s going to be a very close election.”Looming over the political environment is the unpopularity of Mr. Biden. Polls show he has recovered from his lowest points over the summer after signing legislation that addressed climate change and senior drug prices. A dip in gas prices helped, too.But his approval remains mired in the low 40-percent range, and gas prices began ticking back up even before the recent decision by Saudi Arabia and Russia to cut oil production.Democrats have repeatedly framed the election as a choice and warned that Republican gains would usher in the return to power of Mr. Trump’s movement.Representative Hakeem Jeffries of New York, chairman of the House Democratic Caucus, said in an interview that it was an urgent priority to “make it clear that it is an untenable situation to hand over the keys to the extremists in the other party.”Ms. Stefanik, the No. 3 House Republican, accused Democrats of trying to distract voters.Supporters of abortion rights rallied in Wisconsin on the steps of the State Capitol in Madison. Democrats have made the stripping away of abortion rights a central theme of the midterms. Haiyun Jiang/The New York Times“The Democratic Party is trying to turn this into a referendum on Trump,” she said. “It is not. It is a referendum on Joe Biden.”Even more than Mr. Trump, abortion stands at the center of virtually all Democratic electoral hopes this year. Its persuasive power alarmed Republicans over the summer, especially after Kansans voted against a referendum that had threatened abortion rights in the state and Democrats outperformed expectations in some special elections.Gov. Roy Cooper of North Carolina, the chairman of the Democratic Governors Association, said the breadth of the abortion decision had taken swing voters by surprise, despite years of warnings from advocates and predictions from Mr. Trump himself that his Supreme Court appointees would do just that. The shock, Mr. Cooper said, has not worn off.“I don’t think anyone thought that after their testimony in committee in the U.S. Senate that they would actually vote to turn it on its head,” Mr. Cooper said of Trump-appointed justices.Republicans have sought a delicate two-step on abortion, catering to a base demanding its prohibition and to the political center, which is largely supportive of Roe.In Nevada, Adam Laxalt, the Republican Senate candidate, is broadcasting television ads proclaiming that no matter what happens in Washington, abortion will remain legal in Nevada, attempting to pivot voter attention back to crime and the economy.“Over the last two years, Democrat politicians have done incredible damage to America,” one ad intones. “But one thing hasn’t changed: abortion in Nevada. Why do Democrats like Catherine Cortez Masto only talk about something that hasn’t changed? Because they can’t defend everything that has.”A supporter for John Fetterman, the Democratic Senate candidate in Pennsylvania, at a campaign event in Murrysville, Pa., on Wednesday.Justin Merriman for The New York TimesRepublican fortunes have improved in part through enormous spending by a super PAC aligned with Senator Mitch McConnell of Kentucky, which is funding a $170 million television blitz across seven states that started on Labor Day and is set to continue through the election.Crime has dominated the Republican messaging in Nevada, Wisconsin and Pennsylvania, where the summertime edge held by the Democratic nominee, John Fetterman, over Dr. Mehmet Oz, the Republican nominee, has largely evaporated.“Dangerously liberal on crime,” says one anti-Fetterman ad in Pennsylvania.“This campaign weathered an unprecedented six weeks of attacks,” said Rebecca Katz, a senior strategist for Mr. Fetterman. “And not only are we still standing — we’re still winning.”In a twist for this era of hyperpartisanship, voters could render a number of split decisions between governor and Senate contests in battlegrounds this fall.In Georgia and New Hampshire, incumbent Republican governors are leading in polls, outpacing the Republican nominees for Senate. The opposite is true in Wisconsin, where the Democratic governor is further ahead in polling, as well as in Pennsylvania, where Josh Shapiro, the Democratic governor nominee, is leading.In one recent crime ad, Dr. Oz, the celebrity physician, notably drew a distinction between Mr. Fetterman and Mr. Shapiro. He seemed to be searching for crossover Shapiro-Oz votes. More