Saturday's planned 11 a.m. news conference will be held in New York at the Hilton hotel in Midtown Manhattan.
Friday’s social-media proclamation capped a period of extraordinary uncertainty and mixed signals about Trump’s selection, only days before the Republican National Convention is set to open in Cleveland.
Trump's elevation of Pence, 57, a former House leader and ideological purist who has built a deep well of relationships across the conservative movement, was received enthusiastically in some quarters of the GOP — at least initially having Trump's intended effect of bringing together Republican factions that had been cool to his candidacy.
But Democrats were swift to eviscerate Pence and portray him as a divisive and intolerant ideologue out of touch with the diversifying nation. Presumptive Democratic nominee Hillary Clinton's campaign issued a video attacking Pence on issues related to women's health, gay rights and immigration. The video ends with this message: "Donald Trump and Mike Pence — building a great, big, beautiful wall between America and progress."
For Trump, Pence brings a visceral ideological component to what has been a populist campaign centered around economic grievances and strident nationalism. While Trump avoids social issues on the campaign trail and his positions have evolved over the years, Pence has a history of vocally promoting the agenda of hard-line conservatives, such as opposing same-sex marriage, opposing abortion rights and defunding Planned Parenthood.
Antiabortion activists celebrated Pence's ascension and were hopeful that their priorities would now be at the fore of the national debate. Marjorie Dannenfelser, president of the Susan B. Anthony List, said, "Mike Pence is a pro-life trailblazer, and Mr. Trump could not have made a better choice."
Although the Trump campaign sent strong signals that Pence would be the vice-presidential candidate, Trump insisted late into the evening Thursday that he had not finalized his decision — and he postponed a planned Friday rollout, citing the terrorist attack in Nice, France.
Pence emerged from an intensive vetting process that yielded two other finalists, New Jersey Gov. Chris Christie and former House speaker Newt Gingrich, both of whom Trump praised in a string of media interviews Thursday.
Who is Indiana Gov. Mike Pence?
Throughout the day Thursday, Trump’s campaign aides were preparing to formally announce Pence as the vice-presidential candidate. The governor flew from Indiana to New York in advance of the event, and his allies in Indianapolis prepared for him to withdraw from his reelection campaign as governor. Pence faced a deadline of noon Friday to file papers with the state taking his name off the ballot for governor.
By the time Pence flew to New York, he felt “reassured. It was never not him," according to one Republican briefed on the private talks between Pence and Trump who requested anonymity to discuss them. Campaign chairman Paul Manafort kept in close touch with Pence and his aides throughout the day and night to help soothe any nerves, and he was spotted Friday morning at Pence’s hotel.
Trump arrived back at his home at Trump Tower in the early hours of Friday morning following a red-eye flight from Los Angeles, where he had meetings and fundraisers. He was spotted entering his building near dawn, his blue tie loosened, saying nothing to reporters as he ducked inside.
Kellyanne Conway, a Trump strategist who is also a longtime Pence adviser, said in an interview that the pair would “complement each other in tone and content and style” and dismissed speculation by some political consultants that Pence’s folksy personality would not click with Trump.
“Pence has a very latent and very robust sense of humor that will surface fairly quickly,” Conway said. She also described him as an attack dog ready to take on Clinton at only “five or six decibels” and said that his understated presence would “calm a lot of donors and voters about down ballot.”
Clinton's campaign signaled it was ready for such a brawl. In a statement, campaign chairman John Podesta said, "Pence is the most extreme pick in a generation." He called the Indiana governor an "incredibly divisive and unpopular running mate known for supporting discriminatory politics and failed economic policies that favor millionaires and corporations over working families."
A former six-term congressman and talk-radio host, Pence is a seasoned politician who could help bring together disparate blocs of the Republican coalition. Trump would rely on Pence especially to bring aboard social conservatives and establishment leaders who remain skeptical of, if not outright hostile to, Trump’s candidacy.
Trump had long said he wanted a running mate with governing experience who could help him enact his agenda in Washington, and Pence’s credentials as a former House Republican leader seem to fit the bill.
Pence’s gubernatorial tenure has been marked by controversy over a state law considered by critics to be discriminatory against gays, and he has alienated Democrats, who consider him a rigid and far-right figure.
Pence has not always agreed with Trump’s policy ideas. In December, for instance, the governor criticized Trump’s controversial proposal to temporarily ban Muslims from entering the United States. “Calls to ban Muslims from entering the U.S. are offensive and unconstitutional,” he tweeted.
On trade, Pence and Trump have been on opposite sides. While Trump campaigns as a strident protectionist, opposing the Trans-Pacific Partnership and vowing to renegotiate the North American Free Trade Agreement, Pence has been a proponent of such deals. As a member of Congress, Pence voted for every free-trade agreement that he faced.
Throughout Trump’s weeks-long deliberations over a running mate, his political advisers, including Manafort, urged him to select Pence, people familiar with the discussions said.
Trump's selection of Pence was welcomed on Capitol Hill, with House Speaker Paul D. Ryan (R-Wis.) noting that he and the Indiana governor have been friends for years and that he would "do everything I can" to help the ticket win.
"Mike Pence comes from the heart of the conservative movement — and the heart of America," Ryan said in a statement. "I can think of no better choice for our vice-presidential candidate. We need someone who is steady and secure in his principles, someone who can cut through the noise and make a compelling case for conservatism. Mike Pence is that man."
Praise of Pence also poured in from a galaxy of conservative groups — including the Club for Growth, a group that ran millions of dollars in advertisements opposing Trump during the Republican primaries.
“I’ve been privileged to call Mike a friend for more than 20 years,” Club for Growth President David McIntosh said in a statement. “Members of the Club for Growth have been cheering his principled stands for economic conservatism since he came to Congress."
Brent Bozell, chairman of ForAmerica and a tea party leader, called the selection of Pence "a home run for Donald Trump. It's the best conservatives could possibly want. It's a powerful signal, and a welcomed one. This was a top priority for conservatives, and Trump came through in a smashing manner."
Not every Trump supporter was celebrating, however. Robert Jeffress, a Dallas pastor who has traveled with Trump, said in an email that “some evangelicals like myself are disappointed that Pence caved to pressure from big business on a religious-liberty bill.” That said, Jeffress noted that he is “not disappointed enough to vote for Hillary Clinton. Trump still has my full support.”
Democrats and liberal activists criticized Pence as an ideologue. Chad Griffin, president of the Human Rights Campaign, a leading gay rights advocacy group, called Pence "the face of anti-LGBTQ hate in America."
Pence, Griffin said, "has made attacking the rights and dignity of LGBT people a cornerstone of his political career — not just a part, but a defining part of his career."
Rep. James E. Clyburn (D-S.C.) said Trump was "doubling down on the divisive rhetoric that he has been stressing throughout the campaign" by selecting Pence.
"Pence is someone with whom I've served and I've observed, and I think that his legislative record puts Trump's rhetoric on record," Clyburn said.
Trump is known to value loyalty and those who have supported him from the early days of his unconventional campaign. Unlike Christie and Gingrich, Pence endorsed Trump’s chief primary rival, Sen. Ted Cruz (R-Tex.), shortly before the Indiana primary in May. Although the endorsement was notably tepid and seemed designed to offend Trump as little as possible, Trump and Pence were clearly at odds with each other.
With his comfortable victory in Indiana a few days after that endorsement, Trump effectively clinched the nomination — knocking out his final two opponents, Cruz and Ohio Gov. John Kasich. The sweeping Indiana victory remains a point of pride for Trump that he often celebrates on the campaign trail.
Since then, Trump and Pence have gotten to know each other with a series of visits, the most recent in Indiana this week. They had dinner together Tuesday night and appeared a rally and fundraiser in the Indianapolis area, and on Wednesday their two families gathered at Pence's gubernatorial residence for breakfast. Trump and Pence established trust with each other and developed a warm rapport, according to allies of both men.
Jenna Johnson in New York contributed to this report.