When Rick Santorum officially endorsed his former GOP primary rival Mitt Romney, there was no fanfare, no praise-filled speech, no photo op and no joint press conference.
Instead, the former Republican presidential contender announced his support in a lengthy email sent out shortly before 11 p.m. ET Monday night. Santorum did not actually endorse Romney, the presumptive GOP nominee, until the thirteen paragraph of his late-night email.
"Above all else, we both agree that President Obama must be defeated," Santorum said in the email. "Governor Romney will be that nominee and he has my endorsement and support to win this the most critical election of our lifetime."
But the former senator's tepid praise in his Romney endorsement stands in glowing contrast to bitter criticisms he launched at the former Massachusetts governor during their primary battle.
From "the Etch a Sketch candidate" to "the ultimate flip-flopper" Santorum has swung some stinging attacks at the man he has now endorsed.
"Pick any other Republican in the country," Santorum urged his Wisconsin supporters at a March 25th event. "He is the worst Republican in the country to put up against Barack Obama."
And in Kansas, Santorum called into question whether voters could trust Romney, saying "Governor Romney reinvents himself for whatever the political occasion calls for."
This Santorum-style shift from anti-Romney attack lines for pro-Romney rally cries is a theme that permeates presidential politics.
From Michele Bachmann, who gave her official nod to Romney Thursday, to Newt Gingrich, who threw his support behind his one-time bitter rival upon ending his campaign on Wednesday, some of Romney's biggest opponents are adding their names to his growing list of endorsers.
This shift from adversary to advocate is not new to Romney, nor to presidential politics. The same story rang true in 2008 when then-Democratic contender Hillary Clinton endorsed her primary race rival Barack Obama, eventually becoming his Secretary of State.
Here's a look back at the nasty barbs these now-supporters threw at the men they ended up endorsing.
|Endorser: Newt Gingrich|
Newt Gingrich dropped out of the GOP race on Wednesday and by Thursday had thrown his support behind Romney, telling CNN's Wolf Blitzer "I want to campaign for him."
But in the same interview Gingrich stood by his assault on Romney's trustworthiness that he often launched during his campaign.
"The governor said some things that weren't true," Gingrich said Thursday, defending his earlier assertion that Romney was a liar.
After being buried under attack ads ahead of the Florida primary in January, Gingrich said Romney was "fundamentally dishonest" and launched attacks based on "totally phony history, which [Romney] maniacally continues to repeat."
In January, Gingrich said if Romney became the nominee he would "certainly" endorse him, but that Romney "will have a very, very hard time differentiating himself" from President Obama.
"In the long run the Republican Party is not going to nominate the founder of Romneycare, a liberal Republican who is pro-abortion, pro-gun control and pro-tax increases," Gingrich said of the man he now supports to be the next president. "Ain't gonna happen."
At least not until the convention this summer.
|Endorser: Michele Bachmann|
Five months ago then-GOP presidential candidate Michele Bachmann said Romney "cannot beat Obama." Today, the Minnesota Congresswoman's tone had changed, instead calling him "the last chance we have to keep America from going ... over a cliff."
Bachmann officially endorsed her former rival on Wednesday, saying she was "honored" to support "a man who will preserve the American dream of prosperity and liberty."
But back in December, Bachmann blasted Romney as the only governor in history to enact "socialized medicine."
"His policy is the basis for Obamacare," Bachmann said of Romney's heath care plan in Massachusetts during an interview with ABC's Jon Karl before the Iowa Caucus. "You can't have a candidate who has given the blueprint for Obamacare. It's too identical."
|Endorser: Rick Perry|
Sparks notoriously flew between Romney and Rick Perry during the two dozen GOP debates – think $10,000 bets, hiring illegal immigrants, pink slips – but those months of bickering did not stop Perry from endorsing Romney last week.
After Newt Gingrich ended his campaign, Perry switched his endorsement to Romney, commending the presumptive nominee for earning the GOP nomination "through hard-work, a strong organization, and disciplined message of restoring America."
But before Perry dropped out of the race in late January, he had dubbed Romney a "vulture capitalist" who "worried that he'd run out of pink slips."
"There is something inherently wrong when getting rich off failure and sticking it to someone else is how you do your business and I happen to think that is indefensible," Perry said while campaigning in South Carolina of Romney's tenure as the head of Bain Capital.
Perry blasted Romney for hiring a lawn company that employed illegal immigrants, an issue that first came up during Romney's 2008 presidential bid. Romney has said he was unaware that undocumented immigrants were working for the company he hired.
"Mitt, you lose all of your standing from my perspective because you hired illegals in your home and you knew about it for a year," Perry said at a CNN debate in December. "The idea that you stand here before us and talk about that you're strong on immigration is on its face the height of hypocrisy."
|Endorser: Jon Huntsman|
While former GOP hopeful Jon Huntsman is technically in the "endorser" column for Romney, you'd rarely know it by talking to him.
Since pledging his support for the presumptive GOP nominee, Huntsman has called Romney is "wrong-headed" on China policy, said he has a "trust deficit," accused him of not showing "a whole lot of leadership" and blasted him for not putting forth "big, bold visionary stuff."
"I think we're going to have problems politically until we get some sort of third party movement or some voice out there that can put forth new ideas," Huntsman said on MSNBC in February. "All I can say is I'm looking at the political marketplace and the duopoly is tired and we're stuck in a rut."
Prior to dropping out of the race he was even more critical of the man he eventually endorsed.
"I think he's been on three sides of every major issue of the day," Huntsman told ABC's John Berman in January. "And because of that it's going to be very tough in the end … to be able to make that trust argument to the American people."
Huntsman's call for a third party candidate did sit well with the Republican Party, who uninvited him from a March meeting where he was slated to speak.
|Endorser: Rudy Giuliani|
Former New York City Mayor Rudy Giuliani put off endorsing a Republican candidate until just two weeks ago, after Rick Santorum ended his bid and days before Newt Gingrich bowed out of the race.
His hesitation to support Romney may have been due to the fact that five months earlier he dubbed Romney "a man without a core."
"I've never seen a guy change his positions on so many things, so fast, on a dime," Giuliani said on MSNBC in mid-December.
Giuliani then listed the issues he though Romney has flip-flopped on: abortion, gun control, cap and trade and health care.
Later, on Fox & Friends, the former mayor criticized Romney for being "so darn negative."
"Whoever was out front Mitt would attack, sometimes personal attacks," Giuliani said, reflecting on their rivalry in the 2008 presidential race. "I think this could be hurting him. This is after all a Republican primary and they don't want to see a Republican savaging another Republican."
|Endorser: Mitch Daniels|
Former Mississippi Gov. Mitch Daniels, who turned down a presidential run and is rumored to be a possible vice presidential candidate, held off endorsing in the GOP race until last month.
When he did endorse Romney, his support was rather timid, saying Romney "earned" the nomination and now "deserves" to be supported.
"Mitt Romney has earned our party's nomination and now deserves the support of every American still committed to government that serves the people rather than rules over them," Daniels said in a statement announcing his endorsement.
Days earlier, Daniels lamented that presidential candidates "have to campaign to govern, not just to win." "Romney doesn't talk that way," Daniels said with disappointment.
|Endorser: Hillary Clinton|
The 2008 Democratic primary was, without a doubt, a bitter battle between then-Sens. Hillary Clinton and Barack Obama. As the slugfest wore on into June, the vitriol ramped up.
And while Clinton eventually conceded to Obama and endorsed him as the presumptive Democratic nominee, she slung her fair share of attacks at the eventual president.
"I don't think people want a lot of talk about change," Clinton said, taking aim at Obama's "Hope and Change" slogan during the primary race in December 2007. "I think they want someone with a real record: a doer, not a talker. They don't want false hope, they want real results."
Clinton often criticized Obama as a "talker" who did not have enough experience to be president.
"We've seen the tragic result of having a president who had neither the experience nor the wisdom to manage our foreign policy and safeguard our national security," Clinton said in a speech on foreign policy at George Washington University. "We can't let that happen again."
Clinton angrily scolded Obama for "perpetuating falsehoods" by sending out mailers claiming she suggested the North American Free Trade Agreement was a "boon" to the economy, a statement she never made.
"Shame on you, Barack Obama," Clinton said, apparently furious. "Time and time again you see one thing in speeches and then you have a campaign that has the worst kind of tactics. It is not only wrong but it is undermining core Democratic principles."