Trump's veepstakes: 5 reasons to pick a running mate, from Nikki Haley to Tucker Carlson

With Donald Trump tightening his grip on the Republican presidential nomination in record time, political speculation is moving on to the next big question.

What about his running mate?

Presidential nominees in recent decades have relied on different calculations, and encountered varying degrees of success, in picking which ally or rival or outlier to add to their ticket.

Trump teased Fox News that there was someone "I think I like" but added, "There's no rush to that." Nominees typically wait until close to the national convention or even during it to announce their choice, a timing that creates suspense and gives them maximum flexibility to change their minds.

For now, here are five reasons previous nominees have picked who they did, and what that might signal for Trump this time.

1. Appeal to a key group of voters

Trump tapped Indiana Gov. Mike Pence in 2016 in part because of his standing with white evangelical Christians in the heartland, an important part of the GOP base and one that harbored some reservations about the real-estate developer and reality-TV star from New York.

In 2020, Democrat Joe Biden promised during the primaries to put a woman on the ticket. He chose California Sen. Kamala Harris, who became the first woman of color to be nominated on the ticket of a major party. She helped promote him among both female and Black voters, groups whose enthusiasm has been crucial for Democratic candidates.

And in 1968, Republican Richard Nixon picked a combative Greek-American governor from Maryland, Spiro Agnew, in a bid for support from white ethnic voters, many of whom were accustomed to voting for Democrats.

Did it work? All three of those presidential nominees won the White House, though Agnew ended up resigning during Nixon's second term in a bribery scandal. There was also that fiery break between Trump and Pence over the assault on the Capitol on Jan. 6, 2021, as Electoral College votes were being counted in the re-election race they lost.

What this could mean for Trump: Trump no longer needs help among evangelicals, his standing solidified by his presidential appointments to the Supreme Court that helped overturn abortion rights. This time, he could try South Carolina Sen. Tim Scott, the GOP's highest-ranking Black officeholder, to fortify his surprising gains among Black voters, especially Black men.

He might also target suburban women, who have become important swing voters. The female possibilities for running mate could include Arkansas Gov. Sarah Huckabee Sanders and South Dakota Gov. Kristi Noem.

2. Unify the party

Ronald Reagan first tried to convince former president Gerald Ford to take the No. 2 spot on his ticket in 1980, even though he had challenged Ford for the nomination four years earlier. When those talks collapsed, Reagan turned at the last minute to George H.W. Bush, his top rival for the nomination.

That choice helped heal divisions in the Republican Party for the fall election, although first lady Nancy Reagan, for one, never really forgave Bush for criticizing her husband during the primaries.

In 1960, Democrat John F. Kennedy asked Senate Majority Leader Lyndon Johnson of Texas to join him on the ticket despite the objections of Robert Kennedy, his brother and close adviser. Their partnership was dubbed the Boston-Austin axis, a formidable alliance between liberal Northern Democrats and more conservative Southern ones.

Massachusetts Gov. Michael Dukakis would try to replicate it two decades later by tapping Texas Sen. Lloyd Bentsen for his ticket.

Did it work? Reagan ended up winning easily in 1980, and in 1960 Kennedy prevailed in a narrow victory that included the Electoral votes from LBJ's Texas. But in 1988 Dukakis lost to Bush, then the sitting vice president.

What this could mean for Trump: A choice of his former UN ambassador and final rival, Nikki Haley, could close wounds from the Republican primaries, though their increasingly heated rhetoric against one another may make that alliance less likely. He has dubbed her "birdbrain" and she has called him "unhinged."

For the record, he says he won't pick her, and she says she doesn't want the job.

Florida Gov. Ron DeSantis, a rival in the primaries who has endorsed Trump, albeit anemically, would be a more problematic pick. Article II of the Constitution bars an Electoral College member from voting for both a president and vice president from their home state. That means a Florida elector couldn't vote for Trump for president and DeSantis for vice president, assuming both still claimed to be Florida residents.

3. Shore up a weakness

Democrat Barack Obama in 2008 picked Delaware Sen. Joe Biden, a generation older and with the sort of long experience in Washington, especially on foreign policy, that the first-term Illinois senator lacked.

In 2000, Texas Gov. George W. Bush also reassured some voters worried about his lack of Washington experience, especially on foreign policy, by picking Dick Cheney. He was a former Wyoming congressman and Defense secretary. (By then, Cheney was a business executive living in Texas, so he quietly moved back to Wyoming to finesse the Constitutional complication.)

Did it work? The Obama-Biden ticket and the Bush-Cheney ticket each won two terms in the White House.

What this could mean for Trump: He could reassure some skeptics about his temperament and his populist views by choosing someone less inflammatory and with stronger ties to the political establishment. Iowa Sen. Joni Ernst, say, or Tim Scott.

4. Double down

In 1992, Democrat Bill Clinton chose a running mate not to shore up a weakness but to capitalize on his strengths. LIke Clinton, Tennessee Sen. Al Gore was a moderate from the South and a member of the rising generation.

That strategy has been rare. Most nominees have tried to strike some sort of balance, by region or ideology or age. Still, John Kerry in 2004 picked a fellow senator with a similar mien, North Carolina Sen. John Edwards. (Also working for Edwards: He had been Kerry's rival in the Democratic primaries, and he was from a different region.)

Did it work? The Clinton-Gore ticket won two terms in the White House, but Kerry lost narrowly to George W. Bush.

What it could mean to Trump: He could double-down on the MAGA movement that has been his political signature from the start. Entrepreneur Vivek Ramaswamy defined his bid for the nomination by defending Trump. New York Rep. Elise Stefanik, once viewed as a moderate, now echoes Trump by blasting his legal troubles as a "witch hunt" and referring to the Jan. 6 defendants as "hostages." Arizona Senate candidate Kari Lake and Ohio Sen. J.D. Vance are MAGA loyalists who also have appeared with Trump on the stump.

5. Throw a Hail-Mary pass

Some presidential candidates facing contests that seem steeply uphill have turned to a groundbreaking or unexpected choice of a running mate, someone who can seize the headlines and reshape the narrative, at least for a time.

Democrat Walter Mondale electrified the Democratic National Convention in San Francisco in 1984 by picking Geraldine Ferraro, the first woman nominated on the national ticket of a major party.

In 2008, John McCain made a splash at the Republican National Convention by choosing Alaska Gov. Sarah Palin, little known even among many Republicans. Her swaggering speech energized the convention.

Did it work? Mondale lost to Reagan in an historic 49-state sweep, and McCain was trounced by Obama. In fairness, that could hardly be blamed on their running mates, though both become enmeshed in controversies. After all, they had been chosen for races that already seemed hard to win.

What this could mean for Trump: With a narrow lead in national polls, Trump doesn't seem to need to take the risks of a long pass. That said, he has made a career of upending the conventional wisdom. If he was looking for the unexpected, what about House firebrand Marjorie Taylor Greene? Or Tucker Carlson? Donald Trump Jr. told Newsmax that the media provocateur would "certainly be a contender."

That would shake things up, for sure.

This article originally appeared on USA TODAY: Trump's veepstakes: 5 reasons to pick a running mate. Nikki? Tucker?