President Trump is expected to announce his running mate in the next few days, as Democrats debate whether President Biden should step aside and who should take his place if he does. So, how will the Democratic turmoil affect Mr. Trump’s pick?

The Trump campaign is keeping its decision — if it’s finalized — close to the vest. The top three contenders being floated are Senator Vance of Ohio, Senator Rubio of Florida, and North Dakota’s governor, Doug Burgum.

“By this time next Monday, we could know who President Trump has selected as his running mate for the 2024 election,” the Trump campaign’s senior adviser, Jason Miller, said Monday on “Fox & Friends.” He continued, “What we don’t know is who President Trump and his running mate will be running against.”

In light of the Democratic flux, some Republicans are calling on Trump to select a moderate running mate like Virginia’s governor, Glenn Youngkin. They say he could then bring aboard independents who were on the fence before Mr. Biden’s disastrous debate performance. 

“If we win Virginia, we win,” Senator Graham said on CBS’s “Face the Nation” on Sunday. “It is over.”

Nearly three-quarters of Americans think Mr. Biden does not have the cognitive health to serve as president, according to a post-debate CBS poll. Yet despite these headwinds, Mr. Biden had made it increasingly clear he will not drop out of the race. 

“There’s so much instability on the Democratic side, even with who their potential nominee is, that you would think the conventional wisdom is Trump would pick someone who reinforces stability — an established governor or someone with a solid record,” a Republican strategist, Matthew Bartlett, tells the Sun. “But Trump being who he is, I think he will throw caution to the wind, do whatever he wants.”

Mr. Bartlett says he thinks Trump will choose Mr. Vance, a 39-year-old Rust Belt senator whose background embodies the Trump base. A Yale-trained lawyer, Mr. Vance served in the Marines and came to national prominence when his memoir, “Hillbilly Elegy,” became a best seller.

When Trump won in 2016, Mr. Vance made the rounds of cable news programs to explain to the political class what a Manhattan real estate billionaire’s appeal was to the white working class. Originally a critic, Mr. Vance embraced Trump and the populist MAGA movement when he ran for U.S. Senate in 2022. Trump’s endorsement is credited with helping Mr. Vance win a contentious Republican primary.

“I think it will be Vance. Don Jr. wants Vance. Tucker Carlson, Steve Bannon, Charlie Kirk — the list goes on,” Mr. Bartlett says.

Senator Rubio is considered the other top young contender. A 53-year-old Cuban American U.S. senator representing Florida, Mr. Rubio ran for president in 2016 and famously sparred with Trump over the size of his hands and Mr. Rubio’s tendency to sweat. A telegenic, deft communicator, Mr. Rubio has foreign policy experience and could help Republicans win Nevada and Arizona, battleground states with large Latino populations.

“A young generation who can speak fluent Spanish on the campaign trail? He would absolutely make sense,” Mr. Bartlett says.

One possible hitch to Mr. Rubio becoming the nominee is that both he and Trump are Florida residents. Because of the 12th Amendment, Mr. Rubio would need to change his residency, which he has said he is open to doing.

A two-term small-state governor, Mr. Burgum is another finalist for vice president whom Trump has kept close to his side. Mr. Burgum’s campaign for president failed to take off. A successful businessman from small town America, Mr. Burgum is hardly a culture warrior and could appeal to moderates.

Mr. Burgum’s liabilities are that he is 67 years old and he is not as adept at television interviews as Messrs. Rubio and Vance. He also signed a restrictive abortion law in North Dakota that could make his candidacy a non-starter for some suburban women.

Republicans are working hard to appeal to the middle. The Republican National Committee on Monday released its 2024 platform and schedule for next week’s convention. The platform softens the GOP stance on abortion, explicitly leaving restrictions to the states and supporting IVF. The term “traditional marriage” is also scrapped. The phrase “Common Sense” — a term No Labels also adopted when it was considering fielding a ticket — is repeated 12 times in the 16-page streamlined document.

“The new GOP platform is here in an effort to attract moderate voters,” pollster Frank Luntz posted to X.

“I actually wouldn’t be shocked if it’s somebody not on the list the media keeps talking about,” a Republican strategist, Dave Carney, tells the Sun.