RNC Day 3: JD Vance accepts nomination for vice president as Trump watches on

He's 39 and will be 40 by Election Day - by next month, in fact, the same age as Richard Nixon, when he was elected vice president in 1952.

Dan Quayle was elected George H.W. Bush's No. 2 at age 41 in 1988.

But Theodore Roosevelt was only 38 when he was elected vice president and assumed the White House at age 42 after President William McKinley was assassinated in 1901.

Even Roosevelt wasn't the youngest. John C. Breckinridge was just 36 when he took the vice presidency after the 1856 election.

J.D. Vance accepted President Donald Trump's ask to be his 2024 running mate in his primetime speech Wednesday night.

With a kiss to his wife, Vance walked on to the stage. Bowing his head and waving to the crowd, the 39-year-old Ohio senator, elected just 20 months ago, proclaimed, "Wow, wow!" as the crowd briefly chanted "J.D., J.D."

"My name is J.D. Vance, from the great state of Ohio," he said.

To the chance of OH-IO, he said, "We gotta chill with the Ohio, we have to win Michigan too."

He said, "Tonight is a night of hope. A celebration of what America once was, and with God's grace, what it will soon be again."

Vance paid respect to Trump before detailing his own life story.

Beverly Aikins, J.D. Vance's mother, who he writes about in detail in his memoir, is sitting in the Trump family box and receives a standing ovation when Vance mentions her name. He notes that she has been sober for over 10 years.

"Our movement is about single moms like mine, who struggled with money and addiction but never gave up," Vance said.

The Associated Press contributed to this report.

J.D. Vance is speaking in primetime at the RNC, live on all three big networks as well as cable news.

The stakes are high, as this is the first impression many Americans will have of him.

According to a recent YouGov poll, 43 percent of Americans don't have an opinion of Vance -- probably because many of them are hearing about him for the very first time.

This speech will be step one in (he hopes) building a positive reputation for himself.

The conventional wisdom is that presidential candidates should pick running mates who will give them a boost in a key swing state. But Trump didn't do that: Vance is from Ohio, a state that used to be pivotal in presidential elections but has now become pretty reliably Republican. (Trump won it by 8 points in 2020 even as Biden was winning nationwide by a healthy margin.)

Was that a missed opportunity for Trump? Probably not: It turns out that vice-presidential candidates barely matter. Historically, they have been worth about 1 additional percentage point in their home state -- if that -- and don't make a difference in other states. So while Vance might be worth a few extra votes in Ohio, his selection is unlikely to move the needle even in neighboring states such as Pennsylvania and Michigan and probably won't affect the election outcome.

-538's Nathaniel Rakich

Usha Vance, J.D. Vance's wife and political unknown, arrived on the RNC stage for her prime-time debut.

"When I was asked to introduce my husband J.D. Vance to all of you, I was at a loss," she said. "What can I say that hasn't already been said. I mean the man was a subject of a Ron Howard movie."

Vance has left her law firm following her husband being formally announced as former President Donald Trump's running mate at the Republican National Convention on Monday.

Before leaving the firm, Usha's practice focused on "complex civil litigation and appeals in a wide variety of sectors, including higher education, local government, entertainment, and technology, including semiconductors," according to her biography page on the firm's website, before it was removed.

Usha previously served as a law clerk for Chief Justice John G. Roberts, Jr. of the U.S. Supreme Court, Judge Brett Kavanaugh, then of the U.S. Court of Appeals for the District of Columbia Circuit and Judge Amul Thapar, then of the U.S. District Court for the Eastern District of Kentucky, according to the firm.

Born Usha Chilukuri, the wife of the newly announced VP pick, grew up in San Diego, California, and is the daughter of Indian immigrants.

She received her law degree from Yale Law School and, during her time at the institution, served as executive development editor of the Yale Law Journal and managing editor of the Yale Journal of Law & Technology, according to her biography page.

J.D. and Usha met during their time at Yale Law School and got married in Kentucky in 2014, according to the New York Times.

The Associated Press contributed to this report.