Former Vice President Mike Pence on Wednesday called on his party to turn away from what he described as a growing threat of populism led by his former White House boss Donald Trump and "his imitators."

In a speech delivered at the New Hampshire Institute of Politics at Saint Anselm College, Pence said that "Republican voters face a choice" between conservative principles and the rising populist movement within the party.

In his sharpest language to date against the Trump wing of the GOP, Pence said that the populists were substituting limited government and traditional values for "an agenda stitched together by little else than personal grievances and performative outrage."

Pence's speech comes as he vies for the 2024 presidential nomination of a party much changed under the influence of his onetime White House partner. In his address, Pence aimed to create more sunlight between that recent past and his presidential aspirations.

"When Donald Trump ran for president in 2016, he promised to govern as a conservative. And together, we did just that," Pence said in his New Hampshire speech. "But it's important for Republicans to know that he and his imitators in this Republican primary make no such promise today."

The former vice president said that Trump often sounds "like an echo" of President Joe Biden and that Trump was ignoring a coming US debt crisis.

Pence also called out other GOP presidential contenders in his address. He said Florida Gov. Ron DeSantis justifies "using the power of the state to punish a corporation for taking a political stand that he disagreed with" -- a reference to DeSantis' dispute with Disney. He also labeled tech entrepreneur Vivek Ramaswamy, who has risen in the polls in recent weeks, as one of Trump's "populist protégés."

Pence argued in his remarks that populism and conservatism were two competing visions for the future of the GOP -- and that Republicans in 2024 must reject what he described as the "siren song of populism" if they want to be a party of the Constitution.

"The truth is the Republican Party did not begin on a golden escalator in 2015," he said, referencing Trump's splashy entrance that June into the 2016 presidential race at Trump Tower in New York.

The title of Pence's address, "Populism vs. Conservatism: Republicans' Time for Choosing," was a callback to Ronald Reagan's pivotal 1964 speech in support of Barry Goldwater's presidential bid. Pence has modeled himself after the Great Communicator and has cited the conservative late president as the reason he left the Democratic Party as a young man. The second GOP presidential debate is expected to take place at the Ronald Reagan Presidential Library in California later this month.

While Pence has touched on similar themes before, the title of his speech reflects the "inflection point" for the GOP, his advisers said on a Tuesday call with reporters before his address, warning that if the party chooses a presidential nominee who espouses "unprincipled" populist ideas, it could cost Republicans the White House and affect down-ballot races. Pence argued in his speech that conservativism and populism were "unbridgeable," and therefore Republicans must choose their core principles of limited government and the Constitution.

His advisers cautioned that Pence's remarks were not just aimed at Trump or Ramaswamy, with whom Pence tussled at the first GOP presidential debate in Milwaukee over political experience and their visions of the nation, arguing that it would be "much too small an interpretation" of Pence's speech.

The back-and-forth at the debate between Pence, 64, and Ramaswamy, 38, was emblematic of a generational and ideological divide within the party. Since the debate, Pence has continued criticizing Ramaswamy at campaign stops in New Hampshire, taking aim at the Ohio businessman's isolationist "America First 2.0" approach to foreign policy.

Ahead of the speech, Pence's advisers also mentioned South Carolina Sen. Tim Scott and former South Carolina Gov. Nikki Haley, calling them candidates who are positioning themselves as traditional conservatives but who espouse populist views.

"Which might be even more dangerous, because it seems like it's pandering," a Pence adviser said on the Tuesday call with reporters.

Asked how they squared Pence delivering his anti-populist message after having served with Trump, who ushered in a new wave of populism, the advisers said that Trump governed as a conservative, and having Pence as his vice president helped him steer the administration in that direction. Pence's advisers said Trump, who pressured his vice president to reject the 2020 election results and who faces federal charges over his attempt to overturn that defeat, is "not running as a conservative" today.

Pence argued Wednesday that the current course led by populists could lead to a road where "our party's relevancy will be confined to the history books."

"It may live on in some populist fashion, but then it will truly be, in a cruel twist, Republican in name only," he said.

Pence's advisers said the former vice president had approached the speech well aware that populism's appeal is rising, "not just in this race for president, but also in the halls of Congress and in some of the flagship institutions of our conservative movement."

While the latest CNN poll shows Trump with a commanding lead over the rest of the Republican field, Pence's advisers argued that a speech on conservative principles would not come too late.

There's an "important battle right now going on over the future of our party and, in frankly, the future of our nation," they said.

This story and headline have been updated.