A pressure campaign from allies of Donald Trump toward Senate Republican skeptics of some of his Cabinet picks appears to be starting to pay off in a sign of the president-elect's anticipated sway once he enters the Oval Office next month.

Some GOP senators, such Joni Ernst of Iowa and South Carolina's Lindsey Graham, who had been dubious about how they'd vote on Pete Hegseth, the former Fox News host and Trump's pick for Pentagon chief, are sounding more optimistic on getting to "yes," even if they're not quite there yet.

And broader furor around other controversial nominees, including former Democratic Rep. Tulsi Gabbard to be director of national intelligence, Robert F. Kennedy Jr. to lead the Department of Health and Human Services, and Kash Patel to lead the FBI has drawn fewer headlines as the picks meet with senators, though all three are still expected to face tight confirmation processes.

The shifts have come after Trump allies in Washington and in the news media underscored the importance of the president-elect getting his preferred administration in place and shone a glaring spotlight on potential holdouts, making clear that nothing short of their political survival was at stake.

"A month ago, they had running room and courage to oppose Hegseth. They've run out of runway and any courage now is false because the MAGA base is onto them and will make them pay," said one source close to the transition, referencing Trump's "Make America Great Again" mantra.

After it appeared that Hegseth's nomination was on life support, the pressure campaign kicked into high gear.

Trump himself has been more vocal recently about Hegseth, saying on NBC's "Meet the Press" over the weekend that "we'll be working on his nomination" and "I've had a lot of senators calling me up saying he's fantastic." Trump's transition also released what essentially amounted to a hype video Tuesday, touting some senators' glowing remarks about Hegseth.

A conservative group with ties to Elon Musk, the world's richest man who has carved out a powerful role inside Trump's orbit, is also spending $500,000 on a new ad pushing the Senate to confirm Hegseth. The ads push viewers to "call your senator today and urge them to confirm Pete Hegseth" and are airing nationally -- but also targeting digital platforms in Ernst's home state of Iowa.

Those moves, compounded by electoral threats from Trump online media allies like Steve Bannon and Dan Bongino, seem to have moved the needle, even as Hegseth continues to bat away allegations of excessive drinking and sexual misconduct from former colleagues and one woman who claims he raped her.

After predicting there would be "a very thorough vetting before [Hegseth] moves forward," Ernst said after an "encouraging" meeting Monday, "As I support Pete through this process, I look forward to a fair hearing based on truth, not anonymous sources."

Graham, who had cast the claims against Hegseth as serious, also said Monday that he had "a very positive, thorough and candid meeting” with Hegseth and echoed that accusations should be "supported by testimony before Congress -- not anonymous sources."

The movement indicates the immense power Trump and his allies hold, and how influential they could be with the party's base. And the political graveyard is packed with the careers of Republican lawmakers who defied Trump, only to lose office in a primary.

"We will use every resource at our disposal to make sure that every one of Trump's nominees and Cabinet picks are confirmed. And if that does not happen, the ultimate recourse will be at the ballot box for those elected officials who choose to not vote for them," said a second source close to the transition. "That includes Pete, that includes Bobby, that includes Kash, includes everybody."

"We've been very clear. And the president has made calls to various U.S. senators for some of his nominees. The president's been very clear of what he wants. Elon Musk has been very clear," the person added. "When you're the world's richest man, and you have $350 billion, that makes politicians quake."

To be sure, Hegseth himself has also been putting in the work to get confirmed. He's continued to deny the allegations against him, held a blitz of meetings with senators, and Ernst said he committed to appointing a senior official who would tackle the issue of sexual assault within the military.

But the role of Trump's allies can't be dismissed.

The pressure campaign is coming ahead of a new Congress in which Republicans will hold a 53-47 Senate majority, meaning any Cabinet pick cannot afford to lose more than three GOP votes if Democrats vote unanimously in opposition.

Members of Congress are historically fervent in their defense of their role as an equal branch of government -- a role manifested in their "advice and consent" function regarding a president's Cabinet picks. Already, Senate opposition sunk the fortunes of former Rep. Matt Gaetz, R-Fla., Trump's pick for attorney general who had been accused of sexual misconduct that he denied.

Yet Trump has a unique hold on his base, and threats of primaries in cases of disloyalty may be a permanent fixture for lawmakers to prevent opposition to Cabinet picks to mushroom over the next several weeks -- and to enforce support over next four years.

"I think that these senators are very susceptible to pressure because they've witnessed what's happened to members who are now former members who opposed the president. So, we're seeing a lot of members change their tune because they're worried and they don't ever be primaried out of office, and they don't want to have the president having some cross words for them," said Brian Darling, a GOP strategist and former Senate aide.

"Republicans may not appreciate it in the Senate, but it's a fact of life," he added.

Already, damage may have been done for Senate GOP critics, some Republicans warned.

Even if every Republican senator comes around on all of Trump's picks, the president-elect's supporters have long memories -- and the strain of populism that is one of the country's dominant political drivers has piqued anti-incumbent fervor.

"Even her pushback has been noticed in Iowa," Bob Vander Plaats, an influential Christian conservative leader in Iowa, said of Ernst. "You've seen a lot of people push back on her because of it, and there's been some calls from primarily those outside of Iowa going, 'she probably should be primaried.' I haven't seen anything real of that measure in Iowa yet. But it's a primary rich environment today."