His economic expertise and experience as governor could balance John McCain's strength on foreign policy and long tenure in the U.S. Senate. He is a decade younger than the 71-year-old senator and looks younger still.
But Mitt Romney's most valuable role as McCain's running mate could be as rainmaker.
Romney was not only the wealthiest candidate in the 2008 Republican primary field; he also outraised every other contender while he was in the race. And in a year when Republicans are confronting an unprecedented Democratic money machine, Romney's fund-raising prowess could make him especially attractive.
Earlier this month, Romney urged his finance team to contribute to McCain; many of his top donors attended a fund-raiser with President Bush at Romney's vacation home in Deer Valley, Utah on Wednesday night.
In interviews, major Romney donors and fund-raisers said the financial spigots would open much wider if Romney were actually on the ticket.
"There is no doubt in my mind that if Senator McCain selected Governor Romney, there would be a tremendously positive response from those that may not yet be engaged on behalf of Senator McCain," said Thomas R. Tellefsen, a California investor and former national finance chairman for Romney's presidential campaign.
Tellefsen said some Romney donors had not enlisted to help McCain yet because they were new to politics and had a personal connection to Romney. Other supporters said some donors may not be as enthusiastic about McCain as they are about Romney, but a joint ticket might mobilize them.
"You can raise a lot more money if you're passionate about what you're doing," said Ted Welch, a Republican fund-raiser from Tennessee who was a national finance co-chairman for Romney, and who said he raised $155,000 for McCain in the last week.
Some Romney supporters were reluctant to speak publicly about the financial advantage Romney could bring to the GOP ticket, fearing that their comments would be misinterpreted as pressuring McCain to pick him.
"The fact remains that Romney supporters are demonstratively better givers and more aggressive givers" than supporters of other primary candidates this year, one Romney donor said. "But nobody's going to come out and say anything to make it look like they're putting Senator McCain into a corner. .. John McCain is a fiercely independent individual who's going to pick what his gut tells him to pick.".
Other supporters rejected the notion that Romney's wealth or fund-raising ability should be a factor.
"Sure, he would be helpful, but I don't think John McCain will ask him to be vice president for that," said Mel Sembler, a former ambassador to Italy and a former member of Romney's finance team.
The former Massachusetts governor has made it clear he plans to raise money for Republicans regardless of whether McCain picks him as his vice presidential nominee. Romney is now spending most of his time traveling around the country headlining fund-raisers for Republican candidates. And he has not raised any money to repay the $44.6 million he loaned his campaign and has no plans to do so, said Eric Fehrnstrom, a spokesman for Romney's new political action committee, Free and Strong America.
Romney's personal fortune, built during his years as a corporate executive with Bain & Co. and Bain Capital, was estimated to be as much as $250 million last summer.
Few other potential GOP vice presidential picks would be as wealthy as Romney. The exceptions would be Michael Bloomberg, mayor of New York, and Meg Whitman, former chief executive of eBay and a leading Romney fund-raiser who is now a McCain campaign cochairwoman. But a vice presidential candidate's wealth would only matter if the ticket opted out of the public financing system, which prohibits candidates from accepting private donations.
Since the post-Watergate reforms of the 1970s, presidential candidates of both parties have relied on public money to finance their general election campaigns. But as he closes in on the Democratic nomination, Barack Obama, who once promised to use public financing, has sent signals he might change his mind in order to take full advantage of the vast online network that has helped him break all presidential fund-raising records. McCain's campaign would not say whether he would follow Obama's suit if the Democrat opted out.
At the end of April, Obama had brought in more than $265 million, compared to nearly $97 million for McCain. Hillary Clinton had raised about $215 million.
In any case, many Romney supporters said his personal wealth is not nearly as important as his fund-raising capacity. In the primary race, Romney proved his ability to reach beyond the usual GOP donor circles, tapping connections in Michigan, where he was born and his father was a beloved governor; in the business world, through his connections at Bain and Harvard Business School; in Utah, where he led the 2002 Winter Olympic Games; and in the Mormon community, where the Romney family's roots go back generations.
"We brought in a lot of new blood, people who hadn't done it before, and who got motivated," Tellefsen said. "That was the secret to our success."
Romney's fund-raising team also distinguished itself through its strong organization and use of friendly competition as motivation. Romney kicked off his campaign by raising more than $6.5 million at a one-day telethon in January 2007, where he invited supporters from across the country to the Boston Convention and Exhibition Center.
"It looked like he really had a very strong organization put together, and organization is really what is a major thrust behind fund-raising," said Travis Thomas, national finance director of the Bush-Cheney 2004 campaign, who has contributed to McCain but is not affiliated with any campaign this cycle. "If he can bring that to the table, well, that would certainly be beneficial."
Many Romney fund-raisers also said that whether McCain chooses him or not, Romney's work on behalf of the ticket could lay groundwork for a future run.
Frank Vandersloot, an Idaho business executive, had never raised money for a presidential candidate before he traveled to Boston for the January 2007 fund-raiser and brought in $250,000 in a matter of hours. Vandersloot said he planned to follow Romney's lead in helping to raise money for McCain, but said he believed Romney had a future in national politics regardless of whether he is the vice presidential nominee. "I think there will be a sequel to this story," he said.