"I am pleased to announce that I have chosen Governor Mike Pence as my Vice Presidential running mate. News conference tomorrow at 11:00 A.M.," the presumptive Republican nominee tweeted.
CNN reported Thursday that Trump had called Pence and offered him the vice presidential slot on his ticket. Pence has accepted.
The pick sets up a stark clash in styles: a brash presumptive nominee with a tendency to freelance into controversies alongside a cautious former congressional leader who's stuck close to conservative orthodoxy since starting his career in talk radio.
Pence took to Twitter shortly after the announcement, saying
, "Honored to join @realDonaldTrump and work to make America great again," and the campaign debut a new logo featuring both names.
Pence's lawyer filed paperwork with the Indiana secretary of state office officially removing him from the governor's race Friday morning.
The Saturday event is currently scheduled to take place in New York Hilton Midtown in Manhattan, the campaign announced, after earlier plans to hold the event in New Jersey.
Trump did his best to keep the drama going Thursday after a frenetic day.
"I haven't made my final, final decision," he told Fox News' Greta Van Susteren Thursday evening. "I mean, I've got three people that are fantastic. I think Newt (Gingrich) is a fantastic person. I think Chris Christie is a fantastic person, been a friend of mine for 15 years. Just a fantastic person. And there's Mike, and Mike has done a great job as governor of Indiana. You look at the numbers, and it's been great -- he's done really a fantastic job. But I haven't made a final, final decision."
But speaking at a fundraiser in Los Angeles later in the evening, Trump said he had made his pick and the campaign was "ready to announce," according to an attendee. Trump, however, did not say whom he had chosen.
On Wednesday, Trump held a series of auditions with Pence and other top contenders including Christie and Gingrich. And on Thursday, despite sources indicating to CNN that Trump was strongly leaning toward Pence, others in his inner circle -- including Trump's son, Donald Jr. -- repeatedly urged caution.
But by early evening, Trump made the offer.
Trump had initially suggested he would wait until the Republican National Convention to unveil his vice presidential choice, but Indiana law forced his hand. Candidates can't run for both federal and state office after July 15, meaning Pence had to withdraw his name from his re-election race for governor.
Pence's attorney Matt Morgan filed the paperwork Friday with the Indiana Secretary of State's, formally withdrawing him from the governor race.
Pence's selection gives Trump a running mate with strong ties to the Republican base -- particularly social conservatives. He was among the first Republicans to embrace the tea party on Capitol Hill. And as governor of Indiana, he faced major political backlash over his decision to sign into law a "religious freedom" measure that infuriated major businesses that saw it as anti-LGBT.
In tapping Pence, Trump adds to the GOP ticket a politician with ties to the Koch brothers and other influential donors who have so far stayed away from Trump.
Pence is seen as a safe political option for Trump, who also considered candidates who mirror his big personality such as New Jersey Gov. Chris Christie and former House Speaker Newt Gingrich. But Pence made clear this week that he's more than willing to play the role of attack dog, strongly criticizing Hillary Clinton during a rally with Trump.
Clinton, Pence told the applauding crowd, "must never become president of the United States."
An endorsement for Trump's rival
Pence had endorsed Texas Sen. Ted Cruz over Trump before Indiana's crucial early May primary -- a contest Trump won, knocking Cruz from the contest and clinching the nomination.
Still, Pence heaped praise on Trump in the WIBC radio interview where he endorsed Cruz, pointing to Trump's focus on Carrier, the Indianapolis air conditioning company that was shipping 2,100 jobs to Mexico.
Pence said Trump has "given voice to the frustration of millions of working Americans with the lack of progress in Washington, D.C."
"Let me be very clear on this race: Whoever wins the Republican nation for president of the United States, I'm going to work my heart out to get elected this fall," Pence said.
He hasn't avoided criticizing Trump, though. He called Trump's attacks on an Indiana-born judge of Mexican heritage "inappropriate," and said his proposal to temporarily ban Muslims from entering the United States was "offensive and unconstitutional."
A test of Trump-Pence chemistry
Pence and his wife, Karen, who is also a close adviser, met on July 2 with Trump in person in New Jersey for more than an hour.
"The Pences enjoyed spending warm, productive time with the Trumps," said Pence spokesman Marc Lotter in a statement the following day. "They talked about policies that are working in Indiana and the future of this country. Nothing was offered and nothing was accepted."
Since then, Pence has repeatedly complimented Trump, vowing to help him in the general election.
"I think he is going to be a great president. I think he is someone who has connected with everyday Americans like no one since Ronald Reagan. I think he has spoken into the frustration and the longings of the American people as no one since the 40th president, and I think you're going to continue to see him do that," Pence told reporters Tuesday after an event in Indianapolis.
He also downplayed his disagreements with Trump on policy.
"Look, I served in Congress for 12 years. I've been a governor for three and a half years. I haven't agreed with every one of my Republican colleagues or Democrat colleagues on every issue," Pence said. "But I'm supporting Donald Trump because we need change in this country, and I believe he represents the kind of strong leadership at home and abroad that will, to borrow a phrase, make America great again."
Already, Pence's orbit had begun blending with Trump's. Kellyanne Conway, a long-time Pence consultant, recently joined Trump's campaign. And Marty Obst, Pence's gubernatorial re-election campaign manager, joined Trump's finance team.
Who is Pence?
Pence, 57, was born in Columbus, Indiana, a town about 40 miles south of Indianapolis, where his father ran a chain of gas stations.
After working as an admissions counselor at his alma mater, Hanover College, a liberal arts school in Madison, Indiana, and earning a law degree, Pence campaigned for Congress in 1988 and 1990 -- but lost to Democratic incumbent Rep. Phil Sharp. Those campaigns featured bitter attack ads, including one from Pence's campaign, featuring a man clad in Arab garb thanking Sharp for America's dependence on foreign oil.
He began rehabilitating his political career with a short essay called "Confessions of a Negative Campaigner."
In it, he argued that "your First Amendment rights end at the tip of your opponent's nose."
"A campaign ought to be about the advancement of issues whose success or failure is more significant than that of the candidate," Pence wrote. "Whether on the left or the right, candidates ought to leave a legacy -- a foundation of arguments -- in favor of policies upon which their successors can build. William Buckley carries with him a purposeful malapropism. 'Don't just do something,' it says, 'stand there.' "
In 1991, Pence became the president of the Indiana Policy Review Foundation, and in 1993 began his own syndicated radio show based in Rushville, Indiana -- performing as a self-described Rush Limbaugh on decaf.
An early tea party ally
He ran again for Congress in 2000, and this time won -- beginning the six-year tenure for which he's best known in Washington.
By 2009, Pence had risen to become the House Republican Conference chairman, a position he occupied as a leader of the party's socially conservative flank.
He was an early ally of the tea party, and chaired the Republican Study Committee. But as governor, Pence struggled in the shadow of Mitch Daniels, his predecessor who backed away from a presidential campaign of his own in 2014.
Pence, a social conservative, stepped into a series of controversies over LGBT rights.
He advocated a constitutional same-sex marriage ban that the Republican-dominated Indiana legislature decided went too far in limiting LGBT rights. Then Indiana became the subject of a media storm in 2010 when Pence signed into law a "religious freedom" measure that would have allowed companies to assert that their exercise of religion had been violated as a defense if sued for turning away customers. It was championed by social conservatives who saw it as a shield against same-sex marriages, but drew complaints from organizations like the NCAA and Salesforce, a major Indianapolis employer, and national scrutiny. It led Daniels' former campaign manager, Bill Oesterle, to openly speculate about recruiting a primary challenger for Pence.
Pushing through tax cuts
Still, Pence successfully shepherded into law a series of tax cuts in Indiana -- slightly reducing the state's income tax and speeding up the phase-out of its inheritance tax. He's also overseen a state budget that's in the black.
In addition, he persuaded President Barack Obama's administration to accept a state-launched alternative to Medicaid as the vehicle for expanded coverage through Obama's signature health care law. That decision led to some criticism from conservatives, but Pence cast it as a victory over the federal government and for state-based solutions.
Pence has had a fraught relationship with Indiana reporters -- not unlike Trump -- fueled in part by his quickly abandoned 2015 plans to launch a state-run news outlet called "Just IN." Once news of the plan broke, Pence downplayed it as little more than a clearinghouse for news released. But plans drafted by his staff cast it as much more than that, citing "Just IN" as a site that would break state government news ahead of traditional journalists.
In joining Trump's ticket, he leaves Indiana Republicans to replace him in what was expected to be a hard-fought re-election battle against Democratic former state House Speaker John Gregg.