Tuesday Briefing: Donald Trump’s Running Mate

Senator J.D. Vance of Ohio, a political newcomer who was once an outspoken critic of Donald Trump, was chosen to be his candidate for vice president.

Trump made the announcement yesterday as Republicans formally nominated him to run for president, and two days after he survived an attempt on his life at a rally in Pennsylvania.

Vance, 39, a former Marine and author of the best-selling memoir “Hillbilly Elegy,” entered the Senate just last year. He harshly denounced Trump during his 2016 campaign, even texting a former Yale roommate that he feared Trump could be “America’s Hitler.”

But after Vance embraced Trump’s lies about a stolen election, Trump supported him in his senate race. After winning his seat, Vance became a reliable pro-Trump voice in Congress. He has shown that he can energize donors, and his youth could help the ticket at a time when voters have deep concerns about the ages of Trump, 78, and President Biden, 81. Here’s what else to know about him.

The assassination attempt: The F.B.I. said it had gained access to the cellphone data of the man who tried to assassinate Trump. Attention remained focused on the Secret Service’s apparent failure to secure the rally site. Here’s the latest.

The race: The latest New York Times/Siena College polls found that Biden is trailing Trump in Pennsylvania and is just slightly ahead in Virginia, two must-win states.