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Donald Trump is choosing Mike Pence as his running mate, NBC News has learned.

Pence, a former congressman and the current governor of Indiana, flew from Indianapolis to the New York area Thursday ahead of a planned Friday morning joint appearance with the presumptive Republican nominee in Manhattan.

But after a truck plowed into a crowd in Nice, France, reportedly leaving dozens dead, Trump said Thursday night that the Friday event would be postponed.

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In light of the horrible attack in Nice, France, I have postponed tomorrow's news conference concerning my Vice Presidential announcement. — Donald J. Trump (@realDonaldTrump) July 14, 2016

Trump maintained during an interview on Thursday evening that he has not made a "final, final decision," although sources with knowledge of the pick told NBC News Pence would be Trump's ultimate choice. He also indicated that he will announce tomorrow when the rescheduled VP announcement will be held.

Pence, who served as a congressman for more than a decade before being elected governor of Indiana in 2012, has been viewed as a frontrunner for the job who could bring governing experience, knowledge of Capitol Hill and conservative credentials to Trump's ticket.

Influential figures within Trump's staff were said to be urging the real estate mogul to pick Pence, whose record of conservative governance could soothe Republicans wary of Trump's unconventional proposals and inexperience in Washington policy-making.

The final decision came after weeks of deliberation and hours of uncertainty on Thursday as rumors about the pick flew while sources in Trump's orbit insisted publicly and privately that no decision had been finalized.

Trump's son, Don Jr., told NBC News in an interview Thursday afternoon that the shortlist is "down to three" -- meaning Pence, Chris Christie and Newt Gingrich -- but that his father would "come up with a decision today."

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The final call came after an unusually public vetting process, with each of the three finalists campaigning alongside the candidate in appearances widely viewed as auditions for the job.

Trump's team was impressed with Pence's fiery performance at a rally in Westfield, Indiana on Tuesday night. The governor and his wife met at their home with the candidate, his son, daughter and son in-law on Wednesday morning, stoking further speculation that he would be Trump's the ultimate choice.

Sources close to Pence and Trump were preparing for the likelihood of a Pence pick early Thursday but warned that the final choice would be made by the candidate alone.

Without confirming that he was not the choice, Gingrich - who had been viewed as the most likely alternative, said in an interview Thursday that "it was a very great honor to be considered" for the job.