WASHINGTON — It’s mourning in America for broad swaths of the GOP.

Republican elected officials from across the political spectrum are struggling to come to grips as Donald Trump's cemented himself as the clear front-runner for their party's presidential nomination, openly fretting about what it would do to both the party and the conservative movement and openly questioning whether he can be stopped.

"He’s in a good position for himself, and I don’t think it would be good for the party at all," Illinois Rep. Adam Kinzinger told Mashable, warning that a Trump nomination would "do huge damage" to both the GOP’s chances at the ballot box and the conservative movement.

“Optimistically we can sell the conservative message but as you sell it as a heartless messenger, which I think Trump is representing, that does longterm damage to the conservative movement,” he said.

Trump's big head — of steam

Trump’s landslide victory in Nevada's caucuses Tuesday night, after earlier wins in South Carolina and Iowa, added an air of inevitability to his campaign that has the establishment panicked.

No presidential candidate has ever lost the party nomination after winning three of the first four states to vote. He has a big head of steam heading into the first big delegate grab next Tuesday, when more than a dozen states head to the polls — many of them anti-establishment conservative strongholds in the South.

That’s alarming both establishment Republicans who see him as an electoral time bomb and movement conservatives who see him as ideologically shallow, unprincipled and dishonest.

Illinois Sen. Mark Kirk, a centrist who is facing a tough reelection battle in a Democratic-leaning state, admitted he was very worried about the impact Trump’s nomination could have on his own chances.

"He’s such a controversial figure. There could always be a surprise with the Donald," he told Mashable.

Sen. Mark Kirk (R-Ill.) faces a tough race and worries about Donald Trump's impact on his reelection chances. Image: Gabriella Demczuk/Getty Images

Michigan Rep. Justin Amash, a hardline conservative who backs Ted Cruz, warned that a Trump nomination could implode the party. He promised not to vote for Trump if he is indeed the party's nominee.

"You’ve got to consider him the favorite at this stage, so it’s concerning. It may lead to a realignment of the two parties," he said, arguing that Trump is "a populist and a nationalist" — but not a conservative.

"I'm really concerned that the reaction from a large segment from our party has been to support someone who doesn’t really care much about our constitution, who seems to believe that the ends justify the means," Amash said.

This race is Trump's to lose.



Unless he has a meltdown in one of the remaining 5 debates, @realDonaldTrump will be the 2016 GOP nominee. — Frank Luntz (@FrankLuntz) February 24, 2016

Mitt Romney, the 2012 Republican presidential nominee, told Fox News on Wednesday that Trump "has the clearest path to become the Republican nominee."

"I think for the other people their path is becoming a slimmer and slimmer opening and they’re having a difficult time communicating to their supporters just how they could become the nominee," he said.

Romney said that Trump needed to release his tax returns soon — an issue that dogged Romney’s own campaign for months — and warned there could be a "bombshell" in his reports without any trace of irony.

Trump fired back.

Mitt Romney,who totally blew an election that should have been won and whose tax returns made him look like a fool, is now playing tough guy — Donald J. Trump (@realDonaldTrump) February 24, 2016

But Trump's big success also yielded his first Capitol Hill support, with Reps. Duncan Hunter of California and Chris Collins of New York endorsing him on Wednesday.

Can a winnowing field actually help?

Anti-Trump Republicans continue to argue that a shrinking field will make it easier to beat the billionaire businessman down the line, claiming he has a hard ceiling of support.

"I still think Marco Rubio has a very viable path to the nomination," Pennsylvania Sen. Pat Toomey, who’s facing a tough reelection battle in a state where Trump could hurt him, said.

But they’re not as certain that will happen as they once were.

Montana Sen. Steve Daines, one of Rubio’s first backers on Capitol Hill, said he thought Rubio could still catch Trump if other candidates drop out fast enough — but that it isn’t clear whether that will happen.

"If we get this thing to a head-to-head battle Marco wins. The question is how you get it there," he said. "It becomes more problematic when we get to all-or-nothing [states] on March 15. It’s important that this field narrows itself before March 15."

But the other candidates and their supporters are making the same argument with hopes that they can become the anti-Trump, and the longer they stay in the harder it becomes to stop The Donald.

"What would be the incentive for either Ted Cruz or Marco Rubio to get out of the race? They’re both doing well enough to stay in it, they’re not really puling away from each other at this point," Amash said.

That could change after Tuesday.

If Cruz can’t show strength across the broad swath of southern states that should be his bread-and-butter and will vote on that day, he may decide that going on isn’t worth it. If he gets beat in his home state of Texas, which polls show might be possible, it’s hard to see how he continues on. But some of Cruz’s more conservative backers, especially those who have strong views against immigration, may be as likely to jump to Trump as Rubio.

John Kasich similarly may not keep campaigning forever if he can’t show some strength next Tuesday, even though he’s made it clear he wants to stay in until his home state of Ohio votes on March 15.

What Ben Carson does with his single-digit support is anyone’s guess.

Even if this does become a two-man race, Amash warned that doesn’t necessarily make it easier to beat down Trump. Amash said that the "dynamic process" of the race means Trump will pick up voters as well when candidates drop out, and train his attacks on whoever’s left.

Nevada’s results - where Trump won nearly a majority of voters and doubled his nearest competitors — indicate that if Trump has a ceiling he hasn’t hit it yet.

"Even if the race is winnowed down to one-on-one, I think that it’s presumptuous to think that one person would have an easy time against Donald Trump," he said.

Trump agrees.

When Ted Cruz quits the race and the field begins to clear, I will get most of his votes - no problem! — Donald J. Trump (@realDonaldTrump) February 24, 2016

The polls show that I picked up many Jeb Bush supporters. That is how I got to 46%. When others drop out, I will pick up more. Sad but true — Donald J. Trump (@realDonaldTrump) February 24, 2016

Where's the cavalry?

Even those who believe Trump can still be stopped admit that time is running out. A handful of groups have popped up to attack Trump, but none have done so in a sustained way.

Rubio has stuck to attacking Cruz rather than going after the front-runner. Cruz's attacks on Trump come only after months of bear-hugging him, and he still seems more focused on Rubio than the heavy front-runner.

Those candidates who did go after the front-runner did so from a position of weakness, with Graham, Bobby Jindal, Rick Perry and Scott Walker each taking a swing before getting knocked to the mat, as big-money donors mostly sat on their hands and did little to help pay for a campaign against Trump.

Jeb Bush waited too long as his team thought the billionaire would self-implode. By the time he attacked, Trump was rising and had effectively tarred him as "low energy." And as he lost onstage debate fights with Trump, has campaign refused to spend any of its huge war chest on ads to slow down Trump.

"I still think he can be defeated but it’s going to take what frankly should have been going on for the past eight months - some kind of effort to stop him," Republican strategist Doug Heye told Mashable. "There’s been this whole mentality of ‘I’m not going to attack Trump, you should attack Trump.’ It’s a collective problem."

And that early inaction could be disastrous down the road.

"Having a Manchurian candidate become our nominee and potentially president would be very damaging for the Republican Party and for the cause of conservatism," said Heye. "The impact would be severe… We’d probably lose the White House, we have vulnerable House and Senate seats that would be adversely impacted, and there is no moral compass that would tell us what Donald Trump would do in office."