America's "veepstakes" are under way. Running mates have not played a decisive role in helping win the White House in a generation, but will they do so this year?
Democrat Hillary Clinton's presidential bid is positively lackluster when compared to the Donald Trump spectacle, but the ex-secretary of state could give her campaign a jolt with an inspired choice of running mate.
Trump has perhaps the opposite problem; the brash billionaire has never held elected office, and he is believed to be considering seasoned politicians who could provide gravitas to a high-octane campaign.
He recently said he favored choosing someone with government experience who could help him work with Congress.
Here are several potential Clinton and Trump running mates:
Clinton's nomination rival has passionate followers who could give her campaign a boost. She could also embrace parts of 74-year-old Sanders' "political revolution," namely fighting income inequality, that has been his campaign lynchpin.
Sanders is a democratic-socialist, and that could trigger alarm bells.
"One thing the Democrats have to worry about is unintentionally mobilizing the Republicans by picking someone scary as vice president" so that GOP voters say "'I'll hold my nose and vote for Trump,'" political science professor Michael Munger of Duke University told AFP.
Feisty Massachusetts Senator Warren is a liberal superstar who can help transfer the Sanders allegiance to Clinton in a heartbeat.
The 66-year-old consumer protection advocate's supporters have pressed her to run for president, but she has demurred.
Would two women on the ticket turn off male voters? "Probably a good chunk of the voters who would be offended by two women are already lost," said St. Louis University professor Joel Goldstein.
As someone who has helped Clinton appeal to young voters and Hispanics on the campaign trail, the former San Antonio mayor and current secretary of housing and urban development earned early VP buzz.
Currently 41, he would be the fourth youngest vice president ever. When asked by CNN if he could be Clinton's running mate, Castro said "that's not going to happen."
"A combination of Castro and Warren, that might be what you're looking for," said Munger, citing Warren's firebrand style and Castro's fresh-faced charisma.
Enter Tim Kaine. The former Virginia governor, 58, serves in the US Senate and sits on the foreign relations and armed services committees.
Kaine is popular in a swing state, speaks fluent Spanish and was on Obama's VP shortlist in 2008.
Some analysts argue Clinton has the Hispanic vote sewn up, and that she should focus on wooing a more volatile voting bloc: white men.
Mark Warner, 61, is a moderate former Virginia governor and current senator.
Tom Vilsack, 65, served eight years as governor of Iowa and is now secretary of agriculture.
Charlie Crist, 59, is a former governor of Florida, perhaps the biggest battleground state of all.
Asked on NBC whom Trump should pick, former Republican vice president Dan Quayle immediately answered Portman, the 60-year-old senator from swing state Ohio.
Portman, whose calm temperament is the opposite of Trump's, served as US Trade Representative and director of the Office of Management and Budget under George W. Bush.
The speaker of the House of Representatives from 1995 to 1999 has broad name recognition -- he ran for president in 2012 -- and would provide vast knowledge about the workings of Congress.
Gingrich, 72, endorsed Trump and told Fox News he was in the "not no" column when it came to the veepstakes.
Trump has said there is a 40 percent chance he will name a former nomination rival as his running mate.
Carson, a 64-year-old retired neurosurgeon, is now in Trump's inner circle and was tasked with helping find potential VP picks. Having been the only African American in the race, he could help Trump with minority issues.
He only quit the race this month, and has said he is not interested in being vice president. But as the popular governor of Ohio and a former congressman, Kasich, 64, could bring Trump establishment experience and help win a crucial swing state.
Trump is underwater when it comes to women voters, and a female running mate could help neutralize the gender debate.
He recently described 61-year-old Oklahoma Governor Mary Fallin, who has a good track record with conservatives, as "fabulous."
South Carolina Governor Nikki Haley, 44, turned a toxic debate after a shooting tragedy into a political launchpad last year by ordering the Confederate flag removed from the state capitol.
Haley, the daughter of Indian immigrants, could also lend Trump credibility on the deeply divisive immigration issue.