Vance is about to speak 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.

-538's Nathaniel Rakich

After introducing his daughter, Kai Trump, at the RNC, Donald Trump Jr. praised the teen for her "incredible work" then said, "Now back to business."

He began his speech addressing the assassination attempt on Trump at Saturday's rally.

"Just days ago, something that once seemed unimaginable became a terrifying reality," he said. "My father came under literal fire as an incredible patriotic rally turned into a tragedy. On a field in Butler, Pennsylvania, a brave firefighter died, others were injured, and as those bullets rained down, we came millimeters away from one of the darkest moments in our nation's history."

He then went after the Biden administration.

"Remember 'Build Back Better?' Instead, we got broke, bumbling Biden," he said. "Nothing is built, nothing is back, and nothing is better. Bridges are collapsing, our credibility is crumbling and our money is worth less and less every single day."

With a photo of Trump with his fist raised at the rally following the shooting on display, Donald Trump Jr. led the crowd in a chant of "Fight! Fight! Fight!"

"And we will fight. We will fight. We will fight with our voices. We will fight with our ideas and on Nov. 5, we will fight with our vote," he said, positing the election as a choice between "America first" and "America last."

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

Multiple Republican senators chased down U.S. Secret Service Director Kimberly Cheatle after they spotted her at the RNC on Wednesday.

Tennessee Sen. Marsha Blackburn was one of the senators and shared a video of the confrontation on her X page, where she accused Cheatle of "stonewalling" them as she refused to respond to their repeated jeers.

"This was an assassination -- you owe the people answers, you owe President Trump answers," Blackburn can be heard saying in the video.

Multiple sources, who verified the authenticity of the video, told ABC News that the Secret Service director was on the suite level of the convention hall.

Blackburn was joined by Sens. John Barrasso, James Lankford and Kevin Cramer in confronting the director at the convention. Their move is unprecedented.

-ABC News' Allison Pecorin and Katherine Faulders