As a second impeachment trial for Donald J. Trump approaches next month, Republicans in states across the country are lining up behind the former president with unwavering support.

Perhaps no state has demonstrated its fealty as tenaciously as Pennsylvania, where Republican officials have gone to extraordinary lengths to keep Trumpism at the center of their message as they bolster the president’s false claims of a “stolen” election.

Eight of nine Republicans in Pennsylvania’s congressional delegation voted to throw out their state’s own electoral votes for President Biden on Jan. 6, just hours after a mob had stormed the Capitol.

A majority of Republicans in the state legislature had endorsed that effort.

And one House member from the state, Scott Perry, was instrumental in promoting a plan in which Mr. Trump would fire the acting attorney general in an effort to stay in office.

In the weeks since the Nov. 3 election, Republicans in Pennsylvania have made loyalty to the defeated ex-president the sole organizing principle of the party, the latest chapter in a rightward populist march repeated across other states. As elsewhere, the Pennsylvania G.O.P. was once led by mainstream conservatives, but it is now defined almost exclusively by Trumpism. It faces major statewide races in 2022, for offices including governor and the Senate, with an electorate that just rejected Mr. Trump in favor of Mr. Biden.

Far from engaging in self-examination, Pennsylvania Republicans are already jockeying ahead of the 2022 primaries to prove that they fought the hardest for Mr. Trump, who, in spite of the losses by his party in the White House, the Senate and the House, still exerts a strong grip over elected Republicans and grass-roots voters.

As the Republican base has shifted — suburbanites leaning more Democratic, and rural white voters lining up behind Republicans over culture-war issues — G.O.P. leaders recognize the extent to which the former president unleashed waves of support for their party. In Pennsylvania, just as in some Midwestern states, a surge of new Republican voters with grievances about a changing America was triggered by Mr. Trump, and only Mr. Trump.

“Donald Trump’s presidency and his popularity has been a big win for the Republican Party of Pennsylvania,” said Rob Gleason, a former chair of the state G.O.P. Even though numerous state and federal courts rejected the Trump campaign’s baseless claims of voter fraud, Mr. Gleason said the belief that the voting was rigged “lingers in the minds of a lot of people.”

He predicted it would drive Republican turnout in upcoming races. He said he had met this week with a prosecutor who “feels the election was stolen” and was pondering a run for a statewide judgeship this year.

Other Republicans are more skeptical that lock-step support of the former president is the best path forward in Pennsylvania, a critical battleground state that is likely to be up for grabs in the next several election cycles.

“We have become, over four years, the party of Trump, and it has been one test after the other,” said Ryan Costello, a former G.O.P. House member from the Philadelphia suburbs who has been critical of Mr. Trump and is exploring a run for Senate. “It is not a sustainable growth strategy to double and triple and quadruple down on Trump when he gets divisive.”

Despite Mr. Costello’s apprehension, most Republicans thought to be mulling runs for Senate or governor have made it clear that they are prepared to pass a Trump loyalty test.

They include members of the Republican congressional delegation, hard-line members of the legislature, and even Donald Trump Jr. The president’s oldest son is the subject of persistent rumors that he will run for high office in the state — mostly because of his ties to Pennsylvania, where he went to prep school and college. The Trump family spent an enormous amount of time campaigning in Pennsylvania in 2020, and as it seeks its next political stage, the state remains a big one.

The transformation of the Republican Party in Pennsylvania has been stark. Less than two decades ago, it was led by political centrists such as former Senator Arlen Specter and former Gov. Tom Ridge, who became the first secretary of homeland security.

Now it is embodied by Mr. Perry, a member of the hard-line Freedom Caucus who won a fifth term in November for his Harrisburg-area seat. His Democratic opponent, Eugene DePasquale, said he lost the race “fair and square.” But he called the Republican congressman’s efforts on behalf of Mr. Trump in a scheme involving the Justice Department “a radical attempt to overthrow the election.”

Mr. Perry, a purveyor of misinformation about the presidential election, acknowledged on Monday his role in introducing Mr. Trump to an official in the Justice Department. That official, Jeffrey Clark, was willing to abet Mr. Trump in pressing Georgia to invalidate its electoral votes for Mr. Biden.

The plan never unfolded. But Mr. Perry, a retired National Guard general who dodged the new metal detectors in the Capitol, rejected calls by Democrats to resign.

Just as resolute in their defense of Mr. Trump were the other Pennsylvania House Republicans who voted to reject the state’s electoral votes for Mr. Biden on Jan. 6. Representative Conor Lamb, a Democrat from western Pennsylvania, said on the House floor that his Republican colleagues should be “ashamed of themselves” for spreading lies that led to the breach of the Capitol. His impassioned speech nearly precipitated a fistfight.

“The Trump people were putting out a message: ‘We better see you publicly fighting for us,’” Mr. Lamb said in an interview this week. “The 2022 midterm is shaping up to be choosing the candidate who loves Trump the most,” he said of G.O.P. primary contests.

But he called that an opportunity for Democrats to talk about issues affecting people’s lives, such as the economy and the pandemic, while Republicans remain fixated on the 2020 election. “They’re making their main political argument at this point based on a fraud; they’re not making it based on real-world conditions,” he said. “The election was not stolen. Biden really beat Trump.”

Mr. Lamb, who has won three races in districts that voted for Mr. Trump, has been mentioned as a contender for the open Senate seat. “I would say I will be thinking about it,” he said.

Apart from the House delegation, much of the Trumpist takeover in Pennsylvania has occurred in the legislature, where Republicans held their majorities in both chambers in November (a result that the party fails to mention in its vehement claims of election fraud in the presidential race).

In contrast to states such as Georgia and Arizona, where top Republican officials debunked disinformation from Mr. Trump and his allies, in Pennsylvania no senior Republicans in Harrisburg pushed back on false claims about election results, some of them created by lawmakers themselves or by Mr. Trump’s lawyer Rudolph W. Giuliani.

A majority of Republicans in the General Assembly urged the state’s congressional delegation in December to reject the state’s 20 electoral votes for Mr. Biden after the results were legally certified. Such was the pressure from grass-roots Trump supporters that the majority leader of the State Senate, Kim Ward, said in an interview last month that if she refused to sign on to such an effort, “I’d get my house bombed tonight.”

The full embrace of Mr. Trump’s lies about a “stolen” election followed months of Republican lawmakers’ echoing his dismissals of the coronavirus threat. Lawmakers who appeared at “ReOpen PA” rallies in Harrisburg in May, flouting masks and limits on crowd sizes, morphed into leading purveyors of disinformation about election fraud after Nov. 3.

One state senator, Doug Mastriano, who is widely believed to be considering a run for governor, paid for buses and offered rides to the “Save America” protests in Washington on Jan. 6 that preceded the breach of the Capitol. Mr. Mastriano has said he left before events turned violent.

As the legislature convened its 2021 session, Republicans recommitted to a hard-line agenda. Lt. Gov. John Fetterman, a Democrat, was removed by the Republican majority as president of the State Senate at a legislative session on Jan. 5. Mr. Fetterman had strenuously objected to Republicans’ refusal to seat a Democratic lawmaker whose narrow victory had been officially certified.

Republicans in the State House are seeking to change how judges are elected to ensure a Republican majority on the State Supreme Court, after the current court, with a Democratic lean, ruled against claims in election fraud cases last year.

Republican lawmakers have also plunged into a lengthy examination of the November election, even though no evidence of more than trivial fraud has surfaced, and courts rejected claims that election officials overstepped their legal mandates.

Republicans announced 14 hearings in the House. Secretary of State Kathy Boockvar, a Democrat, was grilled in the first one last week. Dismissing the series of hearings as a “charade,” she called on Republicans not to sow further distrust in the integrity of the state’s election, which drew a record 71 percent turnout despite a pandemic.

“We need to stand together as Americans,” Ms. Boockvar said in an interview, “and tell the voters these were lies, that your votes counted, they were checked, they were audited, they were recounted many places, and the numbers added up and they were certified.”