A Timeline of Donald Trump and Paul Ryan's Tumultuous Relationship

— -- The latest round of Twitter scorn that Donald Trump has been spewing towards House Speaker Paul Ryan is a low point in an already tumultuous relationship.

Ryan, the Republican leader from Wisconsin, was criticized by some for delaying his endorsement of Trump until after it had become clear he was the nominee, and more recently, has been criticized by some for holding onto his endorsement of Trump in light of the recording of Trump's vulgar comments from 2005.

Here's a review of some of the highs and lows of one of the most controversial partnerships of the 2016 election season.

Feb. 17: Trump Blames Ryan for Romney Loss

"That was the end of that campaign, by the way, when they chose Ryan," Trump said at an event in South Carolina in February during a discussion about Ryan’s work on Social Security. "And I like him. He's a nice person, but that was the end of the campaign."

Ryan brushed off the criticism days later.

"I found it entertaining," Ryan said in an interview with WKOW-TV in the days following. "I think he says things like this all the time."

March 14: Ryan Denounces Violence at Trump Rallies

A sucker-punch at a North Carolina Trump rally and security concerns led to the cancellation of a Trump rally in Chicago later that week, but that didn't stop some violence from breaking out in Illinois, prompting a response from Ryan.

"I think the candidates need to take responsibility for the environment at their events," Ryan said in an interview with radio station WRJN-AM of Janesville, Wisconsin. "There is never an excuse for condoning violence, or even a culture that presupposes it."

Ryan, who did not mention Trump by name, said he saw the "very concerning" images from the rallies that had happened the weekend earlier in Chicago.

April 26: Trump Declares Himself the Presumptive Republican Nominee

After winning all five states in the Republican primaries in Connecticut, Delaware, Pennsylvania, Maryland and Rhode Island, Trump declared himself the presumptive Republican nominee.

At the time, Sen. Ted Cruz and Gov. John Kaisch were both still running. Cruz wouldn’t stop down formally until May 3, and Kasich the following day.

Reince Priebus, the chairman of the Republican National Committee, tweeted that Trump “will be the presumptive @GOP nominee” on May 3 but that didn’t mean that Ryan was on the same timeline.

May 25: Ryan Still Declines to Endorse Trump

After it became more and clearer that Trump was going to be the party's nominee, all eyes were on Ryan to see when he would formally endorse.

"I have no timeline in mind," Ryan told reporters in his office on Capitol Hill about any future announcement.

"We are having productive conversations,” he added. “Our staffs talk virtually every day. We are having good conversations.”

June 2: Ryan Says He’ll Vote for Trump, Counts as Endorsement

It wasn't a ringing endorsement, but it was something.

Ryan said he would vote for Trump in comments that his spokesman later said could be characterized as an endorsement.

In a column in The Janesville (Wisconsin) Gazette, Ryan said that Trump, the GOP's presumptive nominee, can help House Republicans enact their election-year policy agenda if he becomes president.

"I feel confident he would help us turn the ideas in this agenda into laws to help improve people’s lives. That’s why I’ll be voting for him this fall,” Ryan wrote in the op-ed.

June 7: Ryan Calls Trumps comments about Judge ‘Textbook Racism’ but Stands by Endorsement

Federal Judge Gonzalo Curiel became the subject of Trump's ire in June, prompting national conversations about bias and racism, and an outcry of criticism of Trump.

"I regret those comments that he made," Ryan said.

"Claiming a person can't do their job because of their race is sort of like the textbook definition of a racist comment," Ryan continued.

Defending his endorsement of the presumptive GOP nominee, Ryan said Trump is more likely to back the House GOP's election-year policy agenda than Hillary Clinton.

"Do I believe Hillary Clinton is the answer? No, I do not," Ryan said. "I believe that we have more common ground on policy issues of today and we have more likelihood of getting our policies enacted with him than we do with her."

June 14: Ryan Stands Against Muslim Ban Post Orlando Shooting

Trump was quick to congratulate himself about his calls for Muslim ban, but Ryan was quick to correct his own stance.

"This is a war with radical Islam. It's not a war with Islam. Muslims are our partners. The vast, vast majority of Muslims around this country and around the world are moderate. They're peaceful, they're tolerant,” Ryan said.

These comments came after Trump doubled down on his proposed Muslim immigration ban following the Orlando terror attack. Omar Mateen, the gunman who killed 49 people at a gay nightclub in Orlando, was born in New York to Afghan immigrants.

July 19: Ryan Calls for Party Unity at Republican National Convention

Rather than spending much time praising the party's candidate, Ryan called on Republicans to support a reform agenda in a year that voters in both parties want a "clean break from a failed system."

"What does the Democratic Party establishment offer? What is their idea of a clean break? They are offering a third Obama term, brought to you by another Clinton," he said.

Ryan, who has praised Trump’s performance in the GOP primary, had described the election as a “binary choice” between Trump and Clinton, and argued that any effort that doesn’t help Trump will contribute to a Clinton victory in November.

Aug. 3: Trump Not Ready to Endorse Ryan

Trump told The Washington Post, “I like Paul, but these are horrible times for our country. We need very strong leadership. We need very, very strong leadership. And I’m just not quite there yet. I’m not quite there yet.”

Aug. 4: Pence Breaks With Trump to Endorse Ryan

Even if Trump wasn't ready, his running mate Pence was.

“I strongly support Paul Ryan, strongly endorse his re-election,” Pence said in a phone interview on Fox News. “He’s a longtime friend. He’s a strong conservative leader. I believe we need Paul Ryan in leadership.”

“I think what Donald Trump said is he’s not there yet,” Pence said. “These are two men building a good relationship, and I'm very confident, after Donald Trump’s elected president and Paul Ryan is re-elected to Congress and as Speaker of the House, these two men are going to do great things."

Aug. 5: Trump Decides to Endorse Ryan

"We will have disagreements, but we will disagree as friends and never stop working together toward victory," Trump said. "And very importantly toward real change. So, in our shared mission to make America great again, I support and endorse our Speaker of the House Paul Ryan."

Trump initially said that he hadn't decided whether to endorse Ryan, in an echo of Ryan's initial hesitance to endorse Trump, though Ryan ultimately said he would endorse the real estate mogul.