"We're going to be a much bigger party. We're going to be an expanded party," said the normally combative Trump, who even offered a bit of an olive branch to the press, claiming, "I'm becoming diplomatic."
He'll need a lot more talk like that to calm the fears of nervous GOP leaders. Several senior Republicans say they will not support Trump under any circumstances, and the party's 2012 presidential nominee, Mitt Romney, a Trump critic, is expected to deliver pointed remarks about the state of the race this week.
One reason for the rising panic among much of the so-called Republican establishment over Trump's sweeping Super Tuesday victories is that the same erratic style and divisive policies that work so well for him -- calling for mass deportation of undocumented immigrants, a halt on all immigration by Muslims and building a massive wall on the Mexico border -- probably won't work for many of his fellow Republicans running for re-election to Congress this year.
Republicans are defending 24 Senate seats this fall, and losing five of them will mean losing control of the chamber back to the Democrats.
In swing states, including New Hampshire, Wisconsin, Pennsylvania and Ohio, Republican senators and congressmen will need the active support of independents and Democrats -- precisely the kind of voters most turned off by Trump's harsh rhetoric, petty insults, factual errors and hard-line promises.
"We can't have a nominee be an albatross around the down-ballot races," Senate Majority Whip John Cornyn of Texas recently told CNN
. "That's a concern of mine."
Sen. Jeff Flake, a Republican from Arizona, agrees: "It's a concern to have Trump at the top of the ticket, no doubt, for anybody on the ballot."
Flake and Cornyn have cause to be concerned. Consider the plight of Sen. Pat Toomey of Pennsylvania, who won by a razor-thin
2% margin in 2010. Toomey can't win without making inroads among Democrats and independents in the suburbs of Philadelphia and Pittsburgh, but that task will be monumentally harder with the volatile Trump at the top of the ticket.
It gets worse for Toomey, a fiscal conservative who once was president of the anti-tax Club for Growth. Last fall the group ran an ad campaign
attacking Trump before the Iowa caucuses and would have a hard time making peace with the candidate if he becomes the nominee. And just when he most needs the help of a unified local party to help him, Toomey -- who is backing his fellow senator, Marco Rubio, for president -- has already seen one congressman from Pennsylvania decide to back Trump
, and others may do the same.
In New Hampshire, Sen. Kelly Ayotte is fighting off a stiff challenge
by the state's Democratic Gov. Maggie Hassan -- and, like Toomey, is relying on crossover Democrats and independent voters to help her win re-election. That task gets complicated if Trump is the leading Republican at the top of the ticket: She recently called
Trump's initial refusal to disavow an ex-Ku Klux Klan leader "disgusting and offensive."
Sen. Ron Johnson, facing a tough re-election fight
in Wisconsin and trailing in the polls behind ex-Sen. Russ Feingold, is expressing worry about Trump's impact on his race. And two of the highest-ranking Republicans
in the Wisconsin Legislature "say they won't support Trump and would consider voting for a conservative third-party candidate in the general election if he's the nominee," according to the Wisconsin State Journal.
In Ohio, Sen. Rob Portman is explicitly seeking distance: "I'm not a rabble-rousing, red-meat Donald Trump guy," he told
The Washington Post. And Sen. Mark Kirk of Illinois bluntly broke with Trump's anti-immigration rhetoric
: "In a typical Chicago way, to my Mexican-American friends, I would say, 'Donald Trump callate' -- shut up."
An internal memo
from the National Republican Senatorial Committee outlined the danger last fall in a section called "Donald Trump is a Misguided Missile": "Let's face facts. Donald Trump says what's on his mind and that's a problem," the memo says. "Our candidates will have to spend full time defending him or condemning him if that continues."
Nothing about Trump's Super Tuesday wins changes that hard reality. No matter how much the new "diplomatic" Trump tries to mend fences, Democrats have a large body of videos and documented statements showing him using or accepting profanity, inaccuracies, violence at rallies
, bigoted statements
and other rowdy behavior.
That leaves party leaders with a difficult choice: Back Trump's bid and risk losing control of the Senate, or hang onto control of Congress for dear life -- and let Trump stand or fall without help from the establishment for which he has expressed such contempt.