At the GOP's congressional retreat here, some Republicans publicly and privately began warning that they would not unite behind Trump, highlighting the growing rift that threatens to torpedo their chances of retaking the White House and keeping control of the Senate.
"This is a time of turmoil, the likes of which we've never seen no matter how long we've been in the game," said Sen. John McCain, the party's 2008 presidential nominee. He said in an interview that he'd back the eventual nominee but "obviously (Trump) would not be my selection."
"I think I prefer others who have a better grasp in my view of the challenges we face," McCain said, adding that he will stay neutral through the duration of the primary.
Rep. Adam Kinzinger of Illinois said he "would have to do a lot of soul-searching" if Trump became the nominee, suggesting he'd need to separate himself from the top of the ticket. Kinzinger, a Jeb Bush supporter, said he was "very concerned" about the rhetoric from Trump and what it would mean in a general election.
"I think his tone has been bad -- it's not an inclusive tone," said Kinzinger, a leading moderate. "Only 30-something percent, maybe of Americans identify as Republicans, which means to win a national election you have to reach out."
House Speaker Paul Ryan said party leaders would back a Trump nomination, but he made a veiled critique at the divisive rhetoric espoused by the businessman. "We don't want to have another President like this one who divides our country," Ryan told reporters.
The comments underscore the challenge party leaders face as they grapple with a raucous primary that is dominating the airwaves. They want to harness the energy of the grassroots that is powering the candidacies of Trump and Sen. Ted Cruz, while also aiming to broaden their party's image to moderate and swing-state voters who will be essential in the general election.
Nowhere is that more urgent than the race for the Senate, where 24 GOP seats are in contention, including in states like Illinois, Wisconsin, Ohio, Pennsylvania, New Hampshire and Florida. To stay in the majority, Republicans need to ensure they lose no more than four seats if they don't win back the White House.
Speaking to reporters here at a Marriott hotel on the waterfront, Senate Majority Leader Mitch McConnell suggested that his conference would try to present a more responsible face for voters.
"Our presidential candidates are out there beating each other up at the moment, and that's going to solve itself at some point during the process," McConnell said. By contrast, he said, congressional Republicans are "going to do issue development to try to get ready for 2017."
Haley's SOTU criticism of Trump
McConnell's remarks comments came after the choice of the GOP leader and House Speaker Ryan -- South Carolina Gov. Nikki Haley -- spawned blowback from conservatives over her response to President Barack Obama's State of the Union address this week.
In her speech, Haley urged voters to "resist" the "loudest" and "angriest" voices in the room, comments interpreted as a hit against Trump.
"What she ultimately is trying to do is talk about how do we have a message that's inspiring, inclusive, hopeful, optimistic and that unites the country," Ryan said.
But conservative lawmakers, siding with the anger on talk radio, were frustrated that the party leadership seemed to be undercutting their party's poll leader.
North Carolina Rep. Mark Meadows, a member in the conservative House Freedom Caucus, said Haley was a "very articulate speaker, a very persuasive speaker." But he sharply criticized the move to send a political message to Trump rather than focus on the contrast with the Democrats' agenda.
"When you bring politics into it, even on our side of it, I think the American people don't want that -- whether you are an unaffiliated voter, Democrat of Republican they want it to be about what affects them on Main Street not necessarily what affects those who end up in Washington, D.C."
Democrats look to benefit
As the GOP divide becomes more pronounced, Democrats see an opening to score some political points. Senate Minority Leader Harry Reid, D-Nevada, said in a statement Thursday that Republicans should let Trump's proposals come forward for a vote, including his plan to ban Muslims from entering the country.
"If Republicans are afraid to bring their standard-bearer's policies up for votes, Democrats will hold Republicans accountable by seeking floor votes on Trump's policies ourselves," Reid said.
In response, McConnell warned that Republicans would put forward politically sensitive proposals offered by the Democratic leaders: Hillary Clinton and Sen. Bernie Sanders, I-Vermont.
"What's good for the goose is good for the gander," McConnell said.
2016 congressional agenda
The back-and-forth also shows just how much Trump has hijacked the GOP agenda, even as Hill leaders try to promote a different face for their party.
Oklahoma Rep. Tom Cole, an ally of party leaders, said congressional Republicans are very mindful that whoever the nominee is "going to be is the most important single factor in whether or not we retain majorities in the Senate and the House."
"Sooner or later it's going to be about why you are mad, but what are you going to do," Cole said, adding that "telling everyone it's going to be 'awesome or great and huge' is not going to cut it all the way through November."
Multiple Senate and House Republicans who CNN spoke to in Baltimore stressed the importance of the party creating and promoting a specific agenda to contrast with Democrats.
Republicans huddled in several sessions to discuss efforts to come up with their own alternative health care reform proposal, a major overhaul of the tax code, and their goal of passing all spending bills in order to avoid another massive year-end package.
They also discussed ways to contrast their national security message, and efforts to potentially draft their own authorization for the war against ISIS.
But multiple members and aides said no decisions were made about whether the House and Senate will actually vote on new proposals they intend to unveil in 2016 to contrast with Democrats. On issues like a replacement for Obamacare, rank-and-file members are divided on what needs to be in a bill, and it's unclear they can coalesce around one plan.
When pressed whether Republicans have any reason to believe Trump would listen to their ideas, House Majority Leader Kevin McCarthy, R-California, only said that he'd back the eventual nominee since the GOP is united behind a "philosophy of smaller government."
Still, by promoting conservative ideas, they believe, it will be enough to differentiate Republican lawmakers from the likes of Trump.
"What we are trying to do is ensure that our members are well-positioned to make their argument about why we need to continue to have a Republican majority," said Sen. John Thune, the No. 3 Senate Republican, "irrespective" of what happens on the campaign trail.