Here are a few of the most prominent GOP officials and conservative voices who have fallen in line -- or are at least eyeballing the queue -- behind the presumptive nominee:
Rubio mostly did his best to steer clear of Trump's ire during his since-abandoned primary run. But as the end neared in March, he launched a last-gasp verbal assault on everything from the billionaire businessman's hiring practices to, yup, the size of his hands.
"(Trump) is like 6'2", which is why I don't understand why his hands are the size of someone who is 5'2," Rubio quipped
to supporters at a rally in Virginia. "And you know what they say about men with small hands? You can't trust them."
This particular line of attack led Trump to openly defend the size of his penis
during a nationally televised debate.
But that was then.
Rubio told CNN's Jake Tapper on Thursday he will formally release his delegates to Trump, attend the coronating convention and be willing speak there on behalf of the presumptive nominee.
"I want to be helpful," Rubio said
, offering political aid to the man he once suggested had soiled his pants
during a particularly heated debate.
Rubio's capitulation all but complete, Trump made nice hours later, lending his voice to calls from fellow Republicans for the Florida senator to seek reelection this fall.
"Poll data shows that Marco Rubio does by far the best in holding onto his Senate seat in Florida," Trump wrote. "Important to keep the MAJORITY. Run Marco!"
Paul Ryan: On his way?
No, he has not endorsed Trump. And in comments to reporters on Wednesday, he indicated that, despite the whispers, no formal support is forthcoming.
But the speaker has progressively softened his rhetoric and signaled in a joint statement
with Trump after their recent Capitol Hill kibitz that the GOP's desire to defeat Hillary Clinton makes it "critical that Republicans unite around our shared principles, advance a conservative agenda, and do all we can to win this fall."
It wasn't always so cut and dry. In December, after Trump unveiled his plan to halt the immigration of Muslims into the U.S., Ryan was less inclined to make nice.
"Normally, I do not comment on what's going on in the presidential election. I will take an exception today," Ryan told reporters.
"This is not conservatism," he said of Trump's plan. "What was proposed yesterday is not what this party stands for. And, more importantly, it's not what this country stands for."
Months later, when Trump suggested a contested convention could lead to "riots," Ryan again pushed back sharply.
"Nobody should say such things, in my opinion," he said
at his weekly news conference, "because to even address or hint at violence is unacceptable."
As recently as May 5, just a week before their meeting, Ryan told CNN's Jake Tapper that he was "just not ready"
to back the presumptive nominee. But after their chat -- and with "productive conversations"
ongoing -- an alliance seems inevitable.
Lindsey Graham: One foot on the #TrumpTrain
Late last year, the senior senator from South Carolina told CNN
that Trump was a "race-baiting, xenophobic, religious bigot," who "doesn't represent my party."
But less than six months later, Trump is set to do just that. And the presumptive nominee is increasingly finding a friend in Graham.
They recently enjoyed what the senator described as a "cordial, pleasant phone conversation" and, just this past weekend, Graham encouraged donors
at a fundraiser in Florida to open up their pocketbooks in support of Republican candidates, up and down the ballot -- though not specifically Trump.
(Despite the apparent shift, Graham spokesman Kevin Bishop insisted to CNN that "There hasn't been any change in his position.")
Rick Perry: Curing 'cancer'
Good luck finding a prominent Republican who has executed a swifter and jarring reversal on the prospect of a President Trump.
In a one-week span in July 2015, Perry described
Trump's campaign as a "cancer on conservatism" -- one that "must be clearly diagnosed, excised and discarded."
In a statement
released few days earlier, he referred to "Trump-ism" as "a toxic mix of demagoguery and nonsense."
Fast forward to May 2016 and Perry is whistling a different tune about his party's primary champion, even telling CNN he'd be open to serving as Trump's running mate
in the fall.
"I suspect I'm going to be helping him in a myriad ways -- but if it's the vice presidency, if a cabinet position is where he needs somebody with my experience then I'm not going to go back to Texas and say, 'Aw shucks sir, I'm gonna go fishing.' I'm gonna go serve my country," he said last week at the National Rifle Association's annual meeting.
Bobby Jindal: 'Warts and all'
Speaking at the National Press Club in September 2015, the now former Louisiana governor called Trump "a narcissist and an egomaniac."
The general election contest, he continued, had been "practically gift-wrapped" for Republicans, but "now we are flirting with nominating a non-serious, unstable, substance-free candidate."
Jindal dropped out of the race a couple months later, before a single vote was cast, and went mostly quiet for most of the primary season.
Until May, when he announced in a Wall Street Journal op-ed
that he would support Trump, "warts and all."
"I understand why so many of my Republican friends are in denial, while many of my Democratic friends gleefully anticipate and applaud defections," he wrote. "The media is poised to reward those courageous' Republicans ready to do the 'right thing' and endorse Hillary. Count me out."
Chris Christie: First man up
The New Jersey governor was among the first of Trump's vanquished primary foes to grab on to the front-runner's coattails. But Christie didn't always think so highly of his neighbor from New York.
In August 2015, he told
Fox News that Trump wasn't "suited" to the job and lacked the required "temperament."
Trump's Muslim ban plan "a ridiculous position and one that won't even be productive," and then, in New Hampshire after New Year's really dug in.
"Showtime is over," he said, in a clear reference to Trump. "We are not electing an entertainer-in-chief. Showmanship is fun, but it is not the kind of leadership that will truly change America."
Now a likely choice for a cabinet post in a Trump White House, Christie has been selected to run his transition team
. He also makes frequent appearances at campaign events, like a recent fundraiser that made headlines when Trump made a joke about the governor's weight
Bill Kristol: Define 'never'
The conservative pundit and Weekly Standard editor is still pushing for Mitt Romney to launch a third party bid and, in a National Review editorial titled "Against Trump," asked
: "Isn't Donald Trump the very epitome of vulgarity? In sum: Isn't Trumpism a two-bit Caesarism of a kind that American conservatives have always disdained? Isn't the task of conservatives today to stand athwart Trumpism, yelling Stop?
But Kristol too has recently showed he might still be willing, eventually, to fall in line behind his party's standard-bearer.
"I mean, I guess never say never," he told
Steve Malzberg of Newsmax on May 2. "On the one hand, I'll say #NeverTrump, and on the other hand, I'll say never say never. I'll leave it ambiguous."
Mitt Romney: Hmmmm ...
Romney, like the Bush family, has remained a steadfast opponent of the Trump campaign, even working (unsuccessfully so far) to recruit a conservative, third party general election challenger.
But the 2012 GOP nominee has flip-flopped on Trump too -- in reverse. For all his tough talk now, Romney courted Trump
, then a de facto leader of the racially charged anti-Obama birther movement, just four years ago.
At a news conference announcing Trump's backing, Romney praised his future foe's "extraordinary ability to understand how our economy works and to create jobs."
Is it a line we could hear again before Election Day? Never say never.