Trump has endorsed Mitt Romney — the man he once called the 'dumbest and worst candidate in history'

President Donald Trump endorsed Mitt Romney in his run for a Senate seat in Utah.
Trump urged people to vote for Romney in 2012, but the two criticized each other heavily during the 2016 election campaign.
The history of their relationship can be seen from Trump's many tweets about Romney over the years.

President Donald Trump endorsed Mitt Romney in his run for a Senate seat in Utah on Monday night.

.@MittRomney has announced ... @ Donald J. Trump

But the two men have a tumultuous history, going back to Romney's 2012 presidential bid, through to Romney being one of Trump's most vocal critics during the 2016 election.

Warm support in 2012

It started initially with Trump endorsing Romney's campaign, while subtly indicating their was popular support for his own presidential run.

Flattering. Over 500 upset ... @ Donald J. Trump

Trump openly encouraged voters to get behind Romney on Twitter and also recorded Romney robo-calls.

Make sure you get out and v... @ Donald J. Trump

Tomorrow#emo#s election will ha... @ Donald J. Trump

Trump's support of Romney seemed unconditional.

I was invited to be with Mi... @ Donald J. Trump

Turning sour after Romeny lost

But immediately after the Romney's election loss, Trump seemed to blame the campaign while maintaining a polite level of respect for the candidate.

This was the Republicans el... @ Donald J. Trump

By the following day, Trump seemed to feel he had been key to Romney's win in six states and the campaign's failure to use him more was the cause of the loss.

Romney campaign used me in ... @ Donald J. Trump

In early 2013, Trump felt Romney lost because he didn't connect with voters.

@ChartrandA Yes, I thought... @ Donald J. Trump

Eighteen months later, as rumours began to swirl about who the 2016 Republican presidential candidates would be, Trump began hitting out at Romney.

I can't believe that Mitt R... @ Donald J. Trump

"@Amber_Sadler22: Donald Tr... @ Donald J. Trump

Their relationship deteriorated in 2015.

Brickbats over Trump campaign

In September, Romney said he didn't believe Trump would become the Republican nominee because the party usually chose a conservative candidate who

Romney, who had considered a 2016 run before ruling it out in early 2015, doubled down on his critique of Trump's "hurtful comments" on a range of topics, including women and Hispanics, just a few weeks later.

.@MittRomney can only spea... @ Donald J. Trump

The situation deteriorated even further between the two in early 2016.

In February, Romney said the reason Trump hadn't released his tax returns must be because they contain some sort of "bombshell."

"Either he's not anywhere near as wealthy as he says he is, or he hasn't been paying the kind of taxes we would expect him to pay," Romney told Fox News.

Outright insults

Trump responded the next day. At a GOP debate he said Romney ran a "terrible campaign, he was a terrible candidate." He also lashed out on Twitter.

Mitt Romney, who was one of... @ Donald J. Trump

This time, Romney responded by invoking William Shakespeare's "Hamlet."

Methinks the Donald doth pr... @ Mitt Romney

On March 3, Romney called Trump a

Here's what I know. Donald ... @ Mitt Romney

"Let me put it plainly," Romney said in a speech that day. "If we Republicans choose Donald Trump as our nominee, the prospects for a safe and prosperous future are greatly diminished."

He also tried to distance himself from his one-time endorsement from Trump, though Trump then claimed Romney had "begged" for his endorsement.

If Trump had said 4 years a... @ Mitt Romney

And Trump responded in kind.

Failed candidate Mitt Romne... @ Donald J. Trump

I am the only one who can b... @ Donald J. Trump

Unfit for office

The war of words continued the next day with Romney saying Trump "would

At a rally later that day Trump called Romney a "spoiled brat" and a "nasty guy."

.@MittRomney was a disaster... @ Donald J. Trump

There were so many tweets from Trump flying around Romney took part in the Mean Tweets segment on "Jimmy Kimmel Live" to poke fun at the situation.

Mitt Romney is a mixed up m... @ Donald J. Trump

Failed presidential candida... @ Donald J. Trump

Over the next few months increasing numbers of Republican candidates pulled and Trump's path to the party nomination became clearer.

But on June 10, Romney said Trump's election would cause "

Mitt Romney had his chance ... @ Donald J. Trump

Once Trump secured the Republican nomination, little was said publicly between the two for months.

Sharp turnaround after Trump won

But it wasn't until after the 2016 election that their relationship obviously changed.

Romney quickly sent his "best wishes" to President-elect Trump and the two met for dinner at the end of November. Afterwards, Romney said he thought Trump

President Trump gave a stro... @ Mitt Romney

And 2018 has seen the relationship come full circle with Trump's endorsement of Romney's Senate bid.