MANCHESTER, N.H. (AP) — Former Vice President Mike Pence cast the 2024 election as a fight for the future of conservatism and called on fellow Republicans to reject the “siren song of populism" championed by former President Donald Trump and his followers.

“Should the new populism of the right seize and guide our party, the Republican Party we’ve long known will cease to exist and the fate of American freedom would be in doubt," Pence said in what his campaign plugged as a major speech at the New Hampshire Institute of Politics at Saint Anselm College Wednesday afternoon.

The speech comes at a critical time for Pence, whose campaign has struggled to build momentum since its launch. Four months ahead of Iowa's kickoff caucuses, Trump remains the race's undisputed frontrunner. Pence, who served four years as Trump's loyal second-in-command, has tried to paint himself as the race's most conservative candidate as he champions policies that have fallen out of favor with many Republican voters.

Pence linked the right's populism — promoting a hard focus on ordinary people's complaints about big government and so-called elites — to progressivism on the left as "fellow travelers on the same road to ruin.”

“The growing faction would substitute our faith in limited government and traditional values with an agenda stitched together by little else than personal grievances and performative outrage," he said.

Pence, who broke with Trump on the storming of the Capitol on Jan. 6, 2021, and refused to go along with his efforts to overturn the results of the 2020 election, continued the more aggressive posture he has taken in recent weeks. He went after the former president repeatedly by name.

He quipped that the Republican Party “did not begin on a golden escalator in 2015," a reference to Trump's campaign launch in New York. He argued that the former president has abandoned the conservative principles that he ran on when Pence was his running mate in 2016.

“When Donald Trump ran for president in 2016, he promised to govern as a conservative. And together we did. But it’s important for Republicans to know that he and his imitators on this Republican primary make no such promise today," Pence said. “The truth is Donald Trump, along with his imitators, often sound like an echo of the progressives they seek to replace."

Trump, responding on his Truth Social site, accused Pence of going to the “Dark Side” after only speaking well of him for years.

“His advisers have led him down a very bad path!” Trump said.

Pence accused Trump and his followers of abandoning U.S. allies abroad with isolationist policies and ignoring the national debt.

He also criticized Florida Gov. Ron DeSantis, Trump's highest-polling rival, for using “the power of the state to punish a corporation for taking a political stand that he disagreed with” in his ongoing feud with Disney, one of the largest employers in the state.

Pence accused Trump and his “imitators” of trying to “blatantly erode our constitutional norms,” referencing Trump’s call last year for “the termination of all rules, regulations, and articles, even those found in the Constitution” over his false claims that the 2020 election was stolen.

“You know there’s already a party that embraces appeasement abroad. There’s already a party that would ignore our national debt. There’s already a party that wants to marginalize the right to life," Pence said at one point, adding that this is “not conservatism. It's Republicanism that prioritizes power over principles.”

Instead, Pence repeatedly hailed the example of President Ronald Reagan, arguing the party must return to his model of limited government, strong national defense and traditional values, including staunch opposition to abortion.

Republicans face a “time for choosing," he said, referencing a famous Reagan speech. “The future of this movement, of this great party, belongs to one or the other – not both. That’s because the fundamental divide between these two factions is unbridgeable.”

The speech comes ahead of the second GOP presidential debate, which will be held in California at the Ronald Reagan Presidential Library.

Pence has hinged much of his campaign on doing well in Iowa, which will hold the Republicans' first nominating contest next January. But he has also spent significant time campaigning across New Hampshire and South Carolina. Saint Anselm College has long been a popular venue for candidates to deliver major speeches.

___ Colvin reported from New York.