Orrin Hatch

Sen. Orrin Hatch, R-Utah, speaks during the Utah Republican Party 2016 nominating convention Saturday, April 23, 2016, in Salt Lake City. T

(Rick Bowmer | AP)

WASHINGTON (AP) -- Congressional Republicans are beginning to accept, and even embrace, an outcome that was once unthinkable: Donald Trump as the GOP presidential nominee.

In the wake of the businessman's commanding wins in five Eastern states this week, a growing number of lawmakers say that Trump is taking on an air of inevitability. Some argue they should get behind him now instead of trying to stand in his way, as some establishment Republicans are still attempting to do by backing various "Never Trump" efforts.

For some lawmakers, supporting Trump is seen as their only hope of stopping the Democrats' likely candidate, Hillary Clinton, in November and ensuring a Democratic president doesn't fill Supreme Court vacancies.

"I don't understand. I mean, it's not 'Never Trump.' It's 'Never Hillary.' Never, never, never, Hillary. Come on. Wake up and smell the coffee," said Rep. Mike Kelly of Pennsylvania, who earlier this week cast his ballot for Trump, along with all members of his large family and 57 percent of Republican primary voters in his state.

"I've never seen a party attack one of its own candidates with this aggressiveness," Kelly said of GOP establishment figures who oppose Trump, blaming it on an elitist Washington attitude out of touch with voters.

Sen. Orrin Hatch of Utah, a respected senior member of the Senate, previously endorsed Jeb Bush and then Sen. Marco Rubio and said he doesn't intend to endorse Trump. But Hatch said Thursday of Trump: "It looks to me like he's going to win and if he does I'm going to do everything in my power to help him."

Some leading Republicans have forecast that a Trump candidacy could spell electoral disaster, help Democrats win back control of the Senate and even cost Republicans seats in the House. They point to Trump's disparaging comments about women and minorities that have contributed to high unfavorability ratings.

Hatch, along with others, disagreed.

"I think he could be great if he'll get serious about being president, and I think he will," Hatch said. "When he gets hit with reality that this is the toughest job in the world, he's a clever, smart guy who I think will want to be remembered for doing good things, so I have a feeling he can make that transition."

To be sure, not all are on board, and some lawmakers cringe at the thought of vulnerable Senate Republicans and candidates getting linked to Trump's controversial stances or attempting to distance themselves from them.

"He's looking more inevitable, yeah. I've been wrong all along," said GOP Sen. Jeff Flake of Arizona, an outspoken Trump critic. "My feeling about Donald Trump is, I don't think that that's our best foot forward at all. And I can't imagine being forced to take some of those positions that he's taken. A ban on Muslims, build a wall and make the Mexicans pay for it, you name it."

It remains uncertain whether Trump will amass the 1,237 delegates needed to clinch the nomination ahead of the Republican convention in Cleveland in July. If he does not, Texas Sen. Ted Cruz hopes to make a play to win the nomination as balloting progresses. Ohio Gov. John Kasich also remains in the race.

On Capitol Hill, Cruz remains an unpopular figure, having disparaged party leaders and led the charge to force a 16-day partial government shutdown in 2013 in a futile attempt to cut off money for President Barack Obama's health care law.

Former House Speaker John Boehner, who resigned last fall under conservative pressure, lashed out at Cruz in comments published Thursday in Stanford University's student newspaper, calling him "Lucifer in the flesh" and saying: "I get along with almost everyone, but I have never worked with a more miserable son of a bitch in my life."

Perhaps partly because of Cruz's unpopularity, it's getting easier to find leading lawmakers speaking publicly in favor of Trump. On Thursday, Trump picked up endorsements from House committee chairmen: Bill Shuster of Pennsylvania, who chairs the Transportation Committee, and Jeff Miller of Florida, who chairs Veterans Affairs.

Sen. Bob Corker, R-Tenn., who heads the Foreign Relations Committee, spoke on the phone with Trump on Thursday and later told reporters they had a good and substantive conversation, though he has no plans to endorse him.

On Trump's foreign policy speech, Corker said: "Let's face it, the foreign policy establishment in Washington hasn't been exactly brilliant in their assessments of things, and I do like the fact that he's challenging that status quo, I really do. ... I think his campaign, like anybody who hadn't been in the public arena before, is evolving."

Rep. Tom Rooney of Florida was a leading Rubio backer, but said now "it's time to move on."

"The people have spoken. The Republican primary electorate has spoken so he deserves the opportunity to be our nominee," Rooney said. "If he screws it up as the nominee and hurts the down-ballot ticket, then he screws it up. But right now the people want him to be the nominee."