Donald J. Trump named Gov. Mike Pence of Indiana as his running mate on Friday, adding to the Republican ticket a traditional conservative who boasts strong credentials with the Christian right, and bringing an end to a vice presidential selection process that seemed at risk of spinning out of control.
Mr. Trump announced the choice shortly before 11 a.m., the time at which he had planned to unveil his selection at an event in Manhattan.
But instead of a showy rollout in a Midtown hotel, Mr. Trump named Mr. Pence as his running mate on Twitter, after abruptly canceling their joint event in the aftermath of the attack in Nice, France, on Thursday evening.
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.
— Donald J. Trump (@realDonaldTrump) July 15, 2016
By choosing Mr. Pence as his partner, Mr. Trump has opted both to bow to political convention and also to gamble on a comparatively untested choice. Mr. Pence cuts a far more generic political profile than Mr. Trump; he is viewed by Republicans in Washington and Indiana as a sturdy and predictable politician.
At the same time, Mr. Pence has a record of hard-line views on cultural issues that Mr. Trump has tended to downplay in the presidential race. In Mr. Pence, Mr. Trump now has a running mate who has advocated for defunding Planned Parenthood and restricting abortion rights, and who signed a religious freedom law that critics said would lead to discrimination against gays and lesbians.
Mr. Trump and Mr. Pence, who have no personal friendship that predates the campaign, are expected to appear together in public on Saturday. The Trump campaign previously committed to a joint interview on the CBS show “60 Minutes.”
Mr. Trump had previously said he considered the circumstances on Friday inopportune for rolling out a major political decision, before reversing course and naming Mr. Pence as his running mate on social media.
Even on Thursday evening, however, with images of bloodshed playing across national television, Mr. Trump did not pause his own political schedule: He addressed a fund-raising event in California and gave multiple television interviews, calling in one for a formal declaration of war by Congress against the Islamic State.
Paul Manafort, Mr. Trump’s campaign chairman, said on Fox News on Friday morning that the presumptive Republican nominee had responded emotionally to the violence in France in deciding to delay a formal event with his running mate.
Yet with Mr. Pence as the favored candidate, Mr. Trump could not afford a long delay in making his decision public. The Indiana governorship is on the ballot in November, and state law required Mr. Pence to file paperwork by noon on Friday in order to withdraw from the race and be replaced on the ballot by another Republican.
Without a public affirmation of his partnership with Mr. Trump, Mr. Pence could have been placed in an uncomfortable position – forced either to end his bid for re-election without an irreversible commitment from Mr. Trump, or to abandon his quest for the vice presidency due to an accident of scheduling.
Mr. Trump appeared to hesitate over his decision throughout the week, flying to Indiana for an extended visit with Mr. Pence, and then summoning several other potential running mates to meet with him in Indianapolis after his private aircraft broke down.
Advisers to Mr. Trump indicated to Republicans in Washington on Wednesday night that they planned to make an announcement with Mr. Pence, but on Thursday both Mr. Trump and his press officers stressed that he could still change his mind. Mr. Trump said Thursday evening on Fox that he had not made a “final, final decision.”
With his bid for national office, Mr. Pence is expected to become the first Indiana governor to pull his name from the ballot and be replaced by another candidate, who will be selected by the Indiana Republican Party.
The election for governor is likely to be competitive: Mr. Pence faced a vigorous challenge from John Gregg, a former speaker of the Indiana House of Representatives, who is a Democrat.
A long list of ambitious Republicans have already signaled they may seek to swoop in and claim Mr. Pence’s spot as the party’s standard bearer, including Lt. Gov. Eric Holcomb; Brian C. Bosma, the speaker of the Indiana House; and two members of Congress, Todd Rokita and Susan W. Brooks.