Donald Trump’s credibility as a Republican kingmaker is on the line in a series of primaries in three states, with the outcome poised to dictate the party’s future for years to come.

Some of the former president’s most prominent endorsed candidates are on shaky ground in Idaho, North Carolina, and Pennsylvania, as polling shows Republican voters could reject Trump’s picks in at least one key nominating contest in each state. A loss Tuesday in any of these closely watched primaries would expose limits to the 45th president’s influence with grassroots conservatives, even amid the high approval ratings he enjoys with this crucial voting bloc.

Simultaneously, the success or failure of the Republicans running under Trump’s banner is expected to shape the GOP in the near and long term. Wins by the former president’s endorsed candidates would further the rise of the populist faction of the party’s governing coalition he has championed; losses would bolster traditionalists and the so-called Republican establishment in states where their strength has been waning.

"If Trump's endorsed candidates lose, as recently happened in Nebraska's GOP gubernatorial primary, it will be another sign of the seeming decline, albeit slow, of the former president's influence over the party," said Jeffrey Brauer, political science professor at Keystone College in northeastern Pennsylvania.

"Especially at the state level," Brauer added, "more Republicans have been willing to at least steer away from Trump and his populism and head in the direction of more traditional Republican/conservative values."

ERIC SCHMITT LEADS MISSOURI GOP SENATE PRIMARY; ERIC GREITENS IN THIRD: POLL

Trump-endorsed candidates are on track to win the vast majority of contests in Idaho, North Carolina, and Pennsylvania. These victories could include the Republican primary for Senate in North Carolina and the primary for governor in Pennsylvania. But the extent of the former president’s power over the GOP will be tested in three critical nominating contests where candidates on whom he has staked his reputation are in trouble.

In Idaho, incumbent Gov. Brad Little is favored to win renomination over Lt. Gov. Janice McGeachin. In North Carolina’s 11th Congressional District, Rep. Madison Cawthorn is vulnerable amid concerted challenges from both state Sen. Chuck Edwards and Michele Woodhouse, a conservative activist and onetime ally. In Pennsylvania, Senate contender Dr. Mehmet Oz is in danger of falling to Kathy Barnette or David McCormick, both of whom have received one of Trump’s signature anti-endorsements.

“Every kingmaker has limits. Look at Georgia for Trump,” conceded Bryan Lanza, a Republican operative who advised the former president during his 2016 campaign and is affiliated with the populist wing of the GOP. Lanza was referencing the Georgia GOP gubernatorial primary, in which Trump’s endorsed candidate, former Sen. David Perdue, is expected to lose to incumbent Gov. Brian Kemp.

Some Republican strategists say Trump’s possible misses in Idaho, North Carolina, and Pennsylvania are simply another reminder that candidates and campaigns matter and that the former president’s endorsement is not a tonic for poor-quality politicians or political operations.

“You can have a Trump endorsement, but it’s not an automatic guarantee of victory,” Republican operative Matt Gorman said, referencing Ohio GOP Senate nominee J.D. Vance as an example of a talented candidate who put an endorsement from Trump to good use. “You still need to run a good race.”

Meanwhile, Lanza emphasized that a loss for Oz in Pennsylvania is not necessarily a loss for conservative populists. “In Pennsylvania, MAGA is clearly going to win,” he said. “I’m just not sure Oz will be a part of the wave.”

Indeed, Barnette is a conservative activist and staunch Trump supporter who is running as the authentic “Make America Great Again” candidate (although there are doubts about her viability in the general election). Even McCormick has aligned himself with Trump and wrapped himself in the “America first” slogan popular with the Trump wing of the GOP.

However, McCormick is expected to govern more as a traditional Republican than a populist. And wins by Little in Idaho or either of Cawthorn’s main challengers in western North Carolina would be a defeat for the populists. For instance, both Edwards and Woodhouse are prepared to support House Minority Leader Kevin McCarthy (R-CA) for speaker should the GOP win the majority in November, while Cawthorn has signaled his vote is in doubt.

Still, even if Trump and the populists suffer stinging defeats in this week’s GOP primaries, the former president’s relationship with grassroots Republicans will likely remain intact. Trump’s approval ratings with GOP voters have been consistently high.

CLICK HERE TO READ MORE FROM THE WASHINGTON EXAMINER

Polling has shown that despite apparent limits to the former president’s influence inside the party in primaries, rejection of his handpicked candidates often does not equal rejection of him personally. For example, Republican voters continue to give Trump high marks in surveys asking their views on whether the former president should seek the White House in 2024.

“The media still has Trump on the brain,” said Republican strategist Doug Heye, who is occasionally critical of the former president. “It’s guaranteed that whatever the results are [on Tuesday,] they will be massively over-interpreted.”