For months, Donald Trump and Sen. Ted Cruz (R-Tex.) played nice while competing for the GOP presidential nomination. Then things turned nasty. Now they've completely devolved, and the two are in open warfare. Here's a timeline of their relationship over the course of the presidential campaign.

March 23: Cruz is the first candidate to announce he’s running for president with a rally at Liberty University in Lynchburg, Va. Trump says that Cruz’s Canadian birthplace could be a “hurdle” to his candidacy.

[It’s official: Cruz announces 2016 candidacy]

June 16: Trump declares his candidacy at Trump Tower in New York, declaring he will be the “greatest jobs president God ever created” and that Mexicans are “rapists” and “drug dealers.”

[Donald Trump begins 2016 bid, citing his outsider status]

June 30: Cruz first defends Trump’s comments on Mexicans after Univision and NBC cut ties with the real estate mogul. “I like Donald Trump. I think he’s terrific,” Cruz says on Fox News. “I think he’s brash. I think he speaks the truth.” Cruz accuses NBC of engaging in “silly” and “wrong” political correctness.

July 3: Cruz salutes Trump for bringing up illegal immigration and says he’s not “going to engage in the media’s game of throwing rocks and attacking other Republicans.”

[Ted Cruz continues to defend Donald Trump on immigration]

July 15: Cruz and Trump meet at Trump Tower in New York. “Ted Cruz called me,” Trump tells MSNBC. “And I don’t know why I’m meeting him, to be honest, but I do have respect for him.” At the meeting, Cruz invites Trump to tour the U.S.-Mexico border later that month.

July 23: Trump visits the border in Laredo, Tex. Cruz can’t make it because of Senate votes.

[Donald Trump makes a Texas-size splash with visit to Mexican border]

Aug. 10: Cruz tells Politico it is “foolish” for other candidates to criticize Trump. Cruz suggests he is buddying up to Trump in an effort to gain the businessman’s supporters.

Aug. 19: Trump mentions Cruz as a possible running mate. "I like Ted Cruz. I like Dr. [Ben] Carson. They’ve been very supportive of me," Trump tells NH1.

Aug. 27: Trump announces that he and Cruz are planning a joint appearance at a Capitol Hill rally against the Iran nuclear deal. “We are talking to Ted Cruz, who is a friend of mine and a good guy, about doing something very big over the next two weeks in Washington,” Trump says.

Aug. 29: Cruz tells WYFF that Trump talking about immigration has helped his own campaign, garnering the Texas Republican “incredible support.”

Sept. 9: The two men attend a rally against the Iran nuclear deal on Capitol Hill. "It is a bit of a romance," Trump tells CNN. "I like him, he likes me.” He tells ABC News that Cruz’s birthplace has been checked out by lawyers, and Cruz is in “fine shape” to run for president. Cruz calls Trump a friend and says he “brings an army of TV reporters” to events.

[Donald Trump, Ted Cruz headline Capitol rally against Iran nuclear deal]

Oct. 12: Cruz tells a crowd in Fort Dodge, Iowa, the main reason he is “grateful” Trump is in the race. “He has framed the central narrative of this Republican primary as who will stand up to Washington. Now, if that’s the central question, the natural next question is who has stood up to Washington,” Cruz says. “And I’ve gotta tell you, I cannot decide a better question to decide this primary than that question right there.”

Nov. 30: “Let me be very clear: I don't believe Donald Trump is gonna be the nominee, I don't believe he's gonna be our president,” Cruz says in Coralville, Iowa, stating he doesn’t want to engage in a candidate-on-candidate “food fight” orchestrated by the media.

Dec. 10: The New York Times obtains audio of a private fundraiser where Cruz questions whether Trump and Ben Carson have the “judgment” to be president.

Dec. 11: Trump goes on the offensive on Twitter and at a rally, saying that “not a lot of evangelicals come out of Cuba.” Cruz is an evangelical Christian whose father was born in Cuba.

Cruz tries to mend things between the two.

Dec. 12: Cruz opens up a 10-point lead on Trump in the Iowa caucuses, his first against the businessman, according to a Des Moines Register poll.

Dec. 13: Trump, on Fox News, calls Cruz a “maniac” who will “never get anything done” as president.

Jan. 5: In an interview with The Washington Post, Trump says Cruz’s Canadian birth could be “very precarious” for the GOP. Cruz tweets a video of the show “Happy Days” in response. He laughs off the comments, blaming the media for not focusing on substantive issues.

Jan. 10: Trump asks an audience in Reno, Nev., to weigh in on Cruz’s eligibility to be president. “Is he a natural-born citizen?” Trump asks, as the crowd bellows “no.”

“Who the hell knows?” Trump asks.

[Donald Trump asks a Reno audience to weigh in on Ted Cruz’s eligibility]

Jan. 13: Cruz goes on the offensive for the first time with a stream of pointed criticism aimed at Trump. Cruz questions Trump’s ability to win a general election, casts doubt on his ability to serve as commander-in-chief and questions his “New York values."

[After months of playing nice, Cruz hits Trump. Then hits him again. And again.]

Jan. 14: Cruz and Trump tangle at the Republican debate. Cruz says Trump is “dismayed” that his poll numbers in Iowa are falling and that he, Cruz, is eligible to be president. Trump hits back at Cruz’s “New York values” comment, talking movingly about the Sept. 11, 2001, attacks.

[The detente between Trump and Cruz is definitely over]

Jan. 16: Cruz continues to hammer Trump, telling reporters Trump’s record doesn’t match what he says as a candidate. Cruz’s campaign releases a 1999 “Meet the Press” clip where Trump calls himself “very pro-choice.” Trump sends out more than a dozen tweets about Cruz, blasting him as “the ultimate hypocrite.” Republicans are increasingly seeing a two-man race between Trump and Cruz.

Jan. 18: As Trump continues to hit Cruz on Twitter, Cruz goes after Trump in front of voters for the first time, telling an audience in Whitefield, N.H., Trump was “nowhere to be found” during the 2013 fight over immigration reform and supported the bank bailouts and government stimulus.

Jan. 19: Cruz tells New Hampshire voters that he likes Trump and doesn’t want to engage in personal attacks, but that he will continue to highlight policy differences between the two.

Jan. 25: Cruz tells a group of Iowa pastors that he is the only candidate who can beat Trump, but warns that if Trump wins Iowa, he could gain momentum and win the nomination. Trump, responding to ads against him from Cruz and a super PAC supporting the candidate, said Cruz is “so nervous” and “such a mess.”

[Cruz: I’m the only candidate who can beat Trump]

Jan. 26: Cruz challenges Trump to a ‘mano a mano’ debate after the businessman said he won’t participate in a Fox News debate Thursday.

Jan. 27: The men go at it, predictably, on Twitter.