MILWAUKEE — Heightened security measures, sweltering 90-degree heat, and the attempted assassination of the GOP’s presidential candidate over the weekend are failing to dampen the mood or temper the optimism of attendees at the Republican National Convention at downtown Milwaukee.

Red MAGA hats and newer color alternatives like gold and white dot the heads of attendees crowding the corridors of the basketball stadium-turned-convention center, the Fiserv Forum. Five prominent Black Republicans made prime-time pitches to African American voters, model Amber Rose made hers to younger voters, a Teamsters chief made his to labor, and the bratwurst at the Fiserv ran out by 8 p.m. last night.

“This is so fun,” a first-time convention goer and North Carolina alternate delegate sporting a red bow tie and seersucker jacket, Alton Absher, tells the Sun. A delegate from South Dakota, Shannon Shields, tells the Sun that the fenced-in protected zone around the stadium felt like the safest place in the country to be. 

“There is a lot of good energy here,” Ms. Shields says. “I think even after the shot heard around the world Saturday with Trump and the assassination attempt, I think the party is really unifying behind him, which is good. We need to come together.”

Among politicos and pundits, there was open discussion and some hushed tones about Trump picking the junior senator from Ohio, J.D. Vance, and that his veep might not expand the party base. Among self-described Reagan conservatives and some so-called liberty Republicans, the Vance pick was also a disappointment and confirmation that the Republican Party’s populist MAGA direction is here to stay.

“I love JD Vance, I just think someone like a Youngkin or Tim Scott might have been able to widen the pool of voters,” a former Westchester Court executive and Republican nominee for governor of New York, Rob Astorino, tells the Sun. Yet he concedes, “I think Trump wins no matter what. I thought that before the assassination attempt, because ultimately voters are worried about whether they can afford the bills for next week.”

Mr. Absher tells the Sun he was hoping Trump would choose Virginia’s governor, Glenn Youngkin, but he supports Trump’s pick nonetheless. “I think what Vance brings to the ticket is communication ability,” he says.

“I’m agnostic on J.D. Vance,” a homeschool mother and alternate delegate from Arkansas sporting a “Trump chick” pin, Margot Herzl, tells the Sun. “He has a really inspiring story and I think he is probably going to be fine. I’ll tell you my main concern is somebody just tried to assassinate Trump and I think that it probably would have been best for him to pick somebody that the deep state likes even less than him.”

Other Republicans celebrated the news.

“He’s young, he’s energetic, he’s down to earth, he resonates with voters. And he’s going to be a great VP,” an Ohio delegate, Allison Zwicker, tells the Sun.

The former Republican candidate for president and, until Monday, possible vice president contender, Vivek Ramaswamy, told reporters Monday that Mr. Vance is “an outstanding choice.” He added that he thinks “a Trump-Vance ticket will be the single most formidable ticket of our lifetime.”

When the Sun asked whether Mr. Ramaswamy will be the libertarian Mr. Trump promised to appoint to his cabinet when he was courting votes at the Libertarian Party convention in May, Mr. Ramaswamy demurred and said he’s now a Republican.

“I think there’s a lot of room for the libertarian movement within the America First movement,” Mr. Ramaswamy told the Sun.

Pundits posted to social media about the 39-year-old Mr. Vance’s “youth and inexperience” — to borrow a phrase from President Reagan — but several delegates who spoke with the Sun called Mr. Vance’s age an asset.

“He’s going to bring in the next generation of hopefully Republican voters,” an alternate delegate from Ohio, Steven Herbik, tells the Sun.

“I think he’s a capable guy. It’s Trump’s choice,” a New Mexico delegate and chief executive of a small air carrier, Allen Weh, tells the Sun. “You see Democrats do identity politics, and we don’t do DEI. So he’s another white guy — big deal.”

“The beard community is very happy,” a former New Hampshire state representative and delegate at the convention, Ross Berry, tells the Sun.

Despite the mixed opinions on Mr. Vance, attendees told the Sun they are pleased that the party is unifying behind Trump, particularly after the shooting. They mentioned Governor Haley’s speaking slot and reports that Trump has edited his speech since the shooting to focus on unity.

The mood on the ground was not retribution but excitement. Delegates mentioned Mr. Biden’s disastrous debate performance, calls for him to drop out, and polls that show Trump is favored to win. Judge Aileen Cannon dismissing the classified documents case against the former president Monday only added to a feeling that Trump and Republicans are on a winning streak.