The 2024 Republican nomination will be wide open, whether President Trump wins reelection next year or not. And several high-profile Republicans are already angling to succeed him.

A bit under five years from now, Trump will either be finishing up his second term, won in 2020, or an ex-president, having lost to the Democratic nominee that year. A natural successor for Trump, 73, would be his vice president, Mike Pence, who has dutifully stayed in the shadows for nearly three years in office behind his considerably more brash and flamboyant boss.

Pence, 60, a former Indiana governor and congressman, has a natural advantage heading into 2024 — his daily working relationship with Trump, whom more than 90% of Republicans support.

But Pence, a cautious career politician, has none of Trump's bravado and bluster, which makes the president so endearing to supporters. And vice presidents have trouble directly succeeding the presidents they served. It's only been done twice, by Vice Presidents Martin Van Buren, in 1836, and George H.W. Bush, in 1988. Several others in recent decades have tried but come up short, including Hubert Humphrey in 1968 and Al Gore in 2000.

Pence has largely, though not entirely, avoided getting embroiled in Trump administration scandals, such as the Ukraine military aid affair that led to the president's impeachment on Dec. 18. Yet, he would hardly have a free ride to the 2024 Republican presidential nomination.

Former U.S. ambassador to the United Nations Nikki Haley, 47, also is considered high on the list. Following the former South Carolina governor's sudden exit from her diplomatic post at the end of 2018, she's been subject to rising speculation over her political plans.

Haley finally made it clear she would not run in 2020 but instead campaign for Trump. But 2024 remains a live possibility, a theory stoked by her vocal defense of Trump in the Ukraine matter, and a memoir that helps keep Haley in the public eye.

In late November, the Dallas County Republican Party sent an invitation to a Dec. 2 $25,000-per-attendee Texas fundraiser headlined by Haley. The e-mail was titled “Road to 2024” and welcomed Haley as a prospective presidential candidate. The local Republican party later changed the invitation's wording, which had been not approved by Haley’s team.

Haley is not the only Trump-world ally with foreign policy experience being eyed for 2024. Senate Majority Leader Mitch McConnell wants to see Secretary of State Mike Pompeo, 55, run for the open Kansas Senate seat to succeed retiring Sen. Pat Roberts, which could serve as a platform for a 2024 White House bid.

Fueling speculation is a report that Trump is seeking a new secretary of state to replace Pompeo, a former House member from Kansas and CIA director, if he ran for the Senate. Potential successors to Pompeo at Foggy Bottom includes two Republican senators long mentioned as 2024 candidates, Tom Cotton of Arkansas and Marco Rubio of Florida, the latter of whom lost to Trump in the 2016 GOP presidential primary fight.

Yet, another senator and 2016 Trump GOP primary foe is raising his profile, Ted Cruz of Texas. The Princeton and Harvard Law School graduate, 49, has made no secret that in 2024 he wants to take another shot at the presidency.

"Look, I hope to run again," Cruz said in September. "We came very, very close in 2016. And it's the most fun I've ever had in my life."

After a bitter primary fight that included Trump slurs against members of his family, Cruz has made his peace with the president and is now a vocal supporter. Cruz has traveled the country and touted the president’s political accomplishments while defending him against Democratic opponents.

Trump has reciprocated by bestowing the nickname him “Beautiful Ted,” and holding a reelection rally for Cruz in 2018 as he faced a strong challenge for his Senate seat by then-Democratic Rep. Beto O'Rourke.

“You know, we had our little difficulties. It got ugly,” Trump told the crowd during a rally for Cruz at the Toyota Center in Houston. "But nobody has helped me more.”

Cruz has subtly upped his public presence in other ways. Over the past year, he received accolades for a beard he grew in fall 2018. Cruz noted O'Rourke's own facial hair on Dec. 18, tweet, "Nice beard," after his former Senate rival dropped his bid for the 2020 Democratic presidential nomination.

Cruz also inveighed forcefully on Twitter against a year-end spending deal he and other critics contend was a gift to lobbyist and a waste of taxpayer money. Cruz, in a Dec. 19 video, blasted the 2,313-page omnibus that cleared Congress and was signed by Trump, avoiding a government shutdown.

"Christmas came early in Washington," the Texas senator said in a six-minute video on Twitter.

"While you were with your family, while you were shopping for Christmas, the lobbyists were spending and spending. I present to you, the massive omnibus bill that Congress is voting on," Cruz said while holding a lit cigar with theatrical flair.