A speech by President Biden on Tuesday could be a signal of how hard the Democrats will fight to protect voting rights. WASHINGTON — The Democratic Party pledged millions for it last week, grass-roots groups are campaigning for it nationwide and, as recently as Friday, Senator Chuck Schumer, the majority leader, said the fight for it had only begun.But behind the brave words are rising concerns among voting-rights advocates and Democrats that the counterattack against the aggressive push by Republicans to restrict ballot access is faltering, and at a potentially pivotal moment.President Biden is expected to put his political muscle behind the issue in a speech in Philadelphia on Tuesday. But in Congress, Democratic senators have been unable to move voting and election bills that would address what many of them call a fundamental attack on American democracy that could lock in a new era of Republican minority rule. And in the courts, attacks on voting restrictions face an increasingly hostile judiciary and narrowing legal options.Texas seems poised, absent another walkout by Democratic legislators, to become the latest Republican-controlled state to pass a sweeping legislative agenda placing new barriers to the ability to cast a ballot. That comes on the heels of a major Supreme Court ruling this month further weakening the one enforcement clause of the Voting Rights Act that remained after the court nullified its major provision in 2012. The decision arrived as advocacy groups were pressing lawsuits against restrictive voting laws enacted in roughly a dozen Republican-controlled state legislatures.“One more arrow has been taken out of the quiver of voting-rights plaintiffs to strike down these new laws passed since the 2020 election,” said Nathaniel Persily, an election-law scholar at Stanford. “And it’s not like they had all that many arrows in the quiver to begin with.”Roughly a dozen Republican-controlled states passed laws this past spring restricting voting or significantly changing election rules, ostensibly in response to President Donald J. Trump’s false claims that voter fraud cost him the November election. Many made it harder to vote early or by mail, banned or restricted drop boxes, shortened early or absentee voting periods or gave more leeway to partisan poll watchers. Some laws made it easier to replace local election officials with partisans, something voting rights advocates say might make it possible even to invalidate or sway election results. Atop that, Republican filibuster threats have bottled up the flagship effort by congressional Democrats to counter such restrictions — a sweeping overhaul of federal election laws and a beefed-up revision of the Voting Rights Act. Despite controlling the Senate, Democrats have failed to unite behind a change in filibuster rules that would allow them to pass the legislation with a simple majority vote. That is a painful reversal for Democrats, who had labeled the bills their top priority, and for Mr. Biden, who said a year ago that strengthening the Voting Rights Act would be his first task in the White House. It also has far-reaching ramifications: The election-overhaul bill would set minimum standards for ballot access, potentially undoing some provisions of the newly enacted laws, and ban gerrymandering just as states begin drawing new boundaries for House seats and local political districts.Democrats worry that failing to act will empower states led by Republicans to impose more restrictions before the 2024 presidential election — a genuine concern, they say, given that Mr. Biden carried the Electoral College by fewer than 43,000 votes in three key states, despite outpolling Mr. Trump by seven million votes nationwide. President Biden said a year ago that strengthening the Voting Rights Act would be his first task in the White House.Samuel Corum for The New York TimesAnd some worry that a Republican Party that still refuses to accept the legitimacy of the last presidential vote sets the stage for a constitutional crisis should red states, or even a Republican-led House of Representatives, contest the next close election. “There’s not a caucus meeting that goes by that our leadership doesn’t talk about S. 1 and how our democracy is on the verge of disappearing,” U.S. Representative John Yarmuth, a Kentucky Democrat who has spent 14 years in the House, said in an interview, using shorthand for voting legislation stalled in the Senate. “There’s plenty to be scared about.”Republicans argue that it’s Democrats who are the threat to democracy. “The Democratic Party wants to rewrite the ground rules of American politics for partisan benefit,” Senator Mitch McConnell, the minority leader, said at a hearing on the bill to overhaul voting laws, called the For the People Act. “It’s hard to imagine anything that would erode public confidence in our democracy more drastically.”Mr. McConnell has called the proposal “a craven political calculation” that shows “disdain for the American people.”In the states, Republican legislators have frequently taken a similar tack, charging that Democrats oppose tightening voting rules because they benefit from voter fraud.More common among voting experts, though, is a view that Republicans, facing unfavorable demographic tides, see their future linked to limiting Democratic turnout. “They’re going to do everything they can to hold on to power, and one essential of that is limiting the Democratic vote,” said Larry J. Sabato, a veteran political analyst and director of the Center for Politics at the University of Virginia. Voting-rights advocates and the Biden administration are not without weapons. Under Attorney General Merrick Garland, the Justice Department has already sued to block voting legislation enacted by the Georgia General Assembly this past spring, and more lawsuits are likely.On Thursday, Vice President Kamala Harris said that the Democratic National Committee planned to spend $25 million before the 2022 midterms to organize and educate voters.And a number of voting rights advocates said they believed that the breadth and the audacity of Republican voting restrictions was igniting a backlash that would power a grass-roots voting movement and increase Democratic turnout in the midterms.“It could well have a significant pushback,” said Miles Rapoport, a senior fellow at the Ash Center for Democratic Governance at Harvard. “The extra motivation of ‘You’re not going to take away my vote’ could end up with very, very heavy turnout come 2022 and 2024.”But voting issues could be a motivator for both parties and, in a highly polarized electorate, the moral high ground can be hard to establish. “I think a lot of this from the other side is political theater,” Representative Briscoe Cain, the Republican House Elections Committee chairman in Texas said in a phone interview on Sunday night. The goal, he said, is to “win elections and make Republicans look bad.”Advocacy groups and Democrats also are in the courts. In Georgia alone, eight lawsuits are challenging Republican election laws enacted in the spring. Marc Elias, a longtime lawyer for Democratic Party interests, is opposing new election laws in seven Republican-dominated states.How badly the Supreme Court ruling will hinder such efforts is unclear. The 6-to-3 decision, covering Section 2 of the Voting Rights Act, made it much harder to attack a voting restriction based principally on its lopsided impact on a minority group.Mr. Elias called the ruling “a terrible decision,” but added that most election lawsuits claim violations of the Constitution, not the Voting Rights Act.Richard L. Hasen, a leading election-law expert at the University of California, Irvine, was less sanguine, arguing that one part of the ruling has given states wide latitude to defend restrictions as necessary to prevent fraud — even if there is no evidence of fraud. Stopping fraud is by far the leading reason cited by Republican legislators sponsoring curbs on voting.“There’s no question that the road is much tougher for voting rights plaintiffs in federal courts,” he said. “These battles will have to be fought within each state, mustering coalitions among business groups, civil leaders and voters from all parties who care about the sanctity of the right to vote.”Legal options also exist outside the federal judiciary. Mr. Elias recently won a suit claiming discrimination against college-age voters in the New Hampshire Supreme Court. The Southern Coalition for Social Justice is challenging North Carolina’s voter ID requirements in that state’s Supreme Court. Demonstrators gathered in Washington, D.C., in June to protest for equal voting rights.Kenny Holston for The New York TimesAnd Alison Riggs, a voting-rights lawyer and co-executive director of the coalition, noted that Congress could easily address concerns with the court’s ruling in any revision of the Voting Rights Act.Mr. Biden’s speech on Tuesday may signal whether he intends to become involved in pushing that legislation and the overhaul of voting laws to passage. Mr. Biden made voting issues a priority in his campaign, but as president he has emphasized bread-and-butter issues like infrastructure spending and coronavirus relief. He was largely absent in June when Democrats in the Senate tried and failed to bring up the For the People Act for debate — in part, perhaps, because even Democrats realized that it must be stripped down to a more basic bill to have a chance of passing.The president is unlikely to have that option again. Over the weekend, a close ally, Representative James E. Clyburn of South Carolina, told Politico that Mr. Biden must push to modify the filibuster so both voting bills could pass.So did civil rights leaders in a meeting with the president on Thursday. “We will not be able to litigate our way out of this threat to Black citizenship, voting and political participation,” Sherrilyn Ifill, the president of the N.A.A.C.P. Legal Defense and Educational Fund, said later. “We need legislation to be passed in Congress.”The consequences of doing that — or not — could be profound, said Dr. Sabato. “If there was ever a moment to act, it would be now, because Republican legislatures with Republican governors are going to go even further as we move into the future,” he said.“For years, Democrats will point to this as a missed moment. And they’ll be right.”David Montgomery contributed reporting. More