Republican National Committee Chairman Reince Priebus on Sunday warned that any effort by conservatives to draft a candidate to run against presumptive GOP nominee Donald Trump would be a "suicide mission for our country".
"What it means is that you're throwing down not just eight years of the White House, but potentially 100 years on the Supreme Court and wrecking this country for many generations," Priebus said.
"And so, I think that's the legacy these folks will leave behind."
A group of anti-Trump Republicans led by 2012 GOP nominee Mitt Romney and conservative commentator William Kristol had begun recruiting candidates to make an independent run for the White House, Fox News reported.
Romney has made personal overtures to Nebraska Senator Ben Sasse, a prominent anti-Trump Republican, and Ohio Governor John Kasich. Inquiries have also been made to businessman and Dallas Mavericks owner Mark Cuban.
"I think they should consider the ramifications of what's going to happen on the Supreme Court, get assurances from Donald Trump that they're satisfied with that would show that he's committed to those conservative justices ... and I think that's the better way to go as opposed to this third party route," he said.
Trump's top ally in the Senate said the New York billionaire would require more policy schooling to earn the confidence of other Republicans and show he was ready to take on likely Democratic presidential nominee Hillary Clinton.
"I think he's going to need to learn. He's going to need to understand really completely ... how complex this world is," Senator Jeff Sessions said.
In particular, Sessions said Trump has much to learn about how to talk about matters of war.
Republican Tom Cole, R-Okla., a onetime Trump critic who nonetheless has vowed to back him in November, called him "a work in progress", more so than most candidates.
"Usually you know a lot more about a candidate because they've run for other things. They've cast votes. They've done things. And he does have a shoot-from-the-hip style."
GOP officials are still trying to determine who should be the leading voice for party barely six months before Americans choose their next president in a likely showdown between Trump and Clinton, a former senator and secretary of state.
Trump and House Speaker Paul Ryan who held a high-profile meeting in Washington last week, represent two Republican factions. Ryan has said he was not yet ready to back Trump.
Trump and Ryan said after their meeting on Thursday that they were committed to unifying the party despite their difference over immigration, Muslim immigrants, taxes, benefit programmes and trade.
The discussion seemed to thaw relations enough to make a reconciliation seem possible, and the men spoke of keeping the lines of communication open and of finding common ground.
Ryan's predecessor as speaker, John Boehner, said he endorsed Trump and Ryan probably was "trying to help shape the direction of Trump's policies".
What concerns many Republicans is the prospect of their backing Trump and then having him stumble over the party's core policy issues.
For example, he once suggested that there should be "some form of punishment" for women who have had abortions. Ultimately, Trump said abortion providers, not women, were the ones who should be punished if abortions were outlawed.
The policy education for Trump and his team appears to be underway.
A few weeks ago, top aide Paul Manafort spent about an hour at the conservative Heritage Foundation Washington as part of what the think tank described as part of an ongoing series of policy briefings for candidates and their advisers.
Other Trump officials have been meeting individual members of the house. Trump himself met senators on the same day he met Ryan, and many emerged describing an open-minded, even earnest candidate.
And lately, Trump has taken to describing his policy proposals as merely "suggestions", but also said he is his own best foreign policy adviser.