Mitt Romney and Ron Paul have proven their friendship on the campaign trail, but would Romney-Paul 2012 be a strong ticket?

Romney, who leads the GOP candidates in caucus wins and delegates, has long been projected as the most likely nominee, but struggles to win the favor of more conservative voters. Paul has a strong following of loyal fans, but trails behind as he steadily picks up delegates from state to state.

The former Massachusetts governor and Texas congressman already get along quite well behind the scenes and have stood up for each other in the past. If Mitt Romney is chosen to be the Republican nominee at the convention in August, however, it's unlikely that Paul would be tapped as a running mate.

Compared to some of the ways other GOP rivals personally attack each other, Romney, 64, and Paul, 76, have developed a personal friendship of kindness and civility. At debates, Paul and Romney rarely go after one another's policy or records in the same harsh way they jump at Newt Gingrich and Rick Santorum. Despite stressful complications from last week's Maine caucus (that originally put Romney barely ahead of Paul and now demands a recount), the two haven't really put each other down over it.

A New York Times article published Thursday notes that Paul's campaign jet broke down in New Hampshire last year, Romney's wife, Ann, offered to let Paul, an aide and one of his granddaughters stay the night at their summer home in Lake Winnipesaukee. Romney also offered Paul his private jet to bring him back home to Texas.

It is a friendship that, by Mr. Paul's telling, Mr. Romney has worked to cultivate, writes Richard A. Oppel, Jr. in the Times. The question is whether it is also one that could pay dividends for Mr. Romney as he faces yet more setbacks in his struggle to capture the 1,144 delegates needed to win the nomination.

The speculation about Romney and Paul comes from more than offering a hand here and there. Paul has defended Romney in the past, lashing out at Republicans who criticize his business record at Bain Capital and others who attacked Romney for stating, I like to be able to fire people.

I think they're unfairly attacking him on that issue because he never really literally said that, Paul told ABC News last month. They've taken him way out of context ... He wants to fire companies.

Paul also hinted at the benefits at a Romney-Paul ticket in a CBS interview with Bob Schiefer on Sunday. When asked if he thought Romney could beat President Barack Obama in the general election as the Republican nominee, he said Romney would have a better chance if he had someone who also appealed to Democrats and independents.

I don't know if anyone noticed but there was a Democrat primary in New Hampshire that had I think close to 3,000 write-ins of Democrats, Paul said. So yes, he can beat Obama but I think he also needs somebody that appeals to Democrats and Independents. And if people look carefully at what I'm talking about, they'll find out that my message has an appeal across the political spectrum.

If Romney and Paul team up, they could have a strong financial advantage over Obama. Romney has raked in more than $56 million to his campaign from top dollar donors like Goldman Sachs and JP Morgan. Paul has brought in an impressive amount of money from in short amounts of time from small donors during his money bombs. As of Dec. 2011, the libertarian raised a little more than $26 million.

Of course, Romney and Paul have both taken jabs at each other. The Texas congressman has called Romney a flip-flopper on issues and a serial hypocrite, and Romney has criticized Paul as a fringe candidate. A lot of their ideologies don't meld.

As the so-called establishment candidate, Romney hasn't deviated too much from Republican talking points. He favors robust defense spending, a strong alliance with Israel, getting touch with China and promoting democracy in the Middle East. Paul, an Air Force veteran and libertarian who often deviates from the standard views of his party, wants to slash millions from foreign aid. Both, however, agree that the U.S. should pull its troops out of Afghanistan.

Also, Paul's name hasn't been floated by top party leaders as a potential running mate. New Jersey Gov. Chris Christie, Florida Sen. Marco Rubio, House Budget Chairman Paul Ryan and Virginia Gov. Bob McDonnell are all names that have been floated as vice presidents for Romney. At the Conservative Political Action Conference last week, which generally gives a sense of how the tea party and more conservative voters feel, Rubio, Christie and Virginia Gov. Bob McDonnell were the more popular picks.

Last November, Romney had dropped New Hampshire Sen. Kelly Ayotte's name as a potential running mate.

There are probably 15 names of people, including Kelly Ayotte, Romney told Fox News. I mean, there are terrific Republicans in the Senate, in the House, in governors' offices.

Romney and Paul's could either hint an endorsement in the future if either one of them quits the race before the convention (much more likely Paul than Romney) or that Romney is thinking of Paul as a potential running mate if he wins the nomination. But considering that Romney likes to tread in safe waters to win over the Republican establishment, he would probably pick a name most of the part supports.