Ambitious American politicians from Lyndon Johnson to George Bush to Joe Biden had to be tapped for vice president to achieve their goal of national political office.
That will again be true if Mitt Romney fills the 2012 GOP ticket with Ohio Sen. Rob Portman, or former Minnesota Gov. Tim Pawlenty.
But one potential Republican running mate already looks like someone who could reach the top on his own; how soon depends on Romney's fate.
He is Marco Rubio, the charismatic Cuban-American U.S. senator from Florida whom many see as the GOP's Barack Obama, a history-making figure who could transform the image of both party and country.
Both are smart, ambitious, enormously attractive figures whose ability to dazzle audiences helped fuel their meteoric political rises.
Like Obama, Rubio has written his autobiography at an early age and seemed to relish the comparison with Obama when moderator David Gregory recently made it on NBC's "Meet the Press."
"Hopefully, in book sales, too," cracked the smiling 41-year-old senator.
But his just-published "An American Son" has yet to reach the lucrative best-selling status of Obama's "Dreams from my Father."
In deciding to seek the Senate in 2010, Rubio disclosed, "I studied his (2004) Senate run."
"I felt that if someone like that can run and win in Illinois, someone like me can win in Florida," he said. (Florida's Cuban-American population is relatively smaller than Illinois' black population, but its overall Hispanic proportion is larger).
Unlike Obama, Rubio achieved major legislative leadership positions. His politics are as conservative as Obama's were liberal, similar to those of GOP colleagues but with a softer edge.
"I've criticized this over-reliance on cutting discretionary spending," Rubio told reporters at a recent Christian Science Monitor breakfast. "You can't get 100 percent of your cuts from 30 percent of your budget."
But, like GOP presidential candidates, he rejected a hypothetical 10-1 balance of spending cuts and tax increases, though one of his political mentors, former Florida Gov. Jeb Bush, recently endorsed it.
"I am in favor of more revenue for government" so it can "pay down the debt and it can fund those essential things that the government should do," Rubio said.
"The problem is that I don't agree with the way that they (Obama and the Democrats) want to generate that revenue," he said. "I think that the way you generate that revenue is through more taxpayers, not through more taxes."
Rubio differs from most Republicans on immigration, an issue he says "will never be solved in a reasonable and a responsible way until it is significantly depoliticized."
He opposes the DREAM Act, which would provide a path to citizenship for young people brought here illegally as children, but was exploring a compromise to help some of them when Obama pre-empted his effort and announced he was suspending deportation of up to 1 million illegal youths, pending enactment of a permanent plan.
Rubio charges that Obama "injected election-year politics into an issue that privately I thought we were making progress on," pointedly noting the White House never contacted him on the issue.
One big question is whether Republicans would nominate a Hispanic, especially one whose Cuban background differs from the Mexican, Puerto Rican and Central American heritage of most Latino Americans. Still, Rubio is looking past 2012 — and the Senate.
"If I do a good job in the Senate, if I'm a serious policymaker, if I take my time to put forward bills as opposed to, you know, bumper-sticker solutions, like I've tried to do with this immigration issue, then I think six years from now, I'll have a lot of opportunities to do different things in politics, outside of politics," he told Gregory.
"My experience has been that if you do a good job at your job, you'll have other opportunities, including some you've never expected."
Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News. Email: firstname.lastname@example.org.