NEW YORK (

MainStreet

) -- Mitt Romney released his 2010 tax returns, and much of the media focus rightly has been on his low tax rate -- due to a combination of charitable tithing and the peculiar way the tax code treats his income from

Bain Capital

, Romney pays an effective rate of just 13.9%.

But the candid look at the candidate's finances has served to remind voters just how filthy, stinking rich the guy is. But like politicians sometimes have short memories ("I do not recall receiving that memo, no"), so too do voters; Romney is far from the richest candidate to run for president in recent decades.

Romney, who made his fortune in management consulting and private equity, boasts a net worth of about $250 million, placing him among the top five richest Americans to run for president in the past 20 years. And while that pile of cash has certainly made it easier for him to run his two presidential campaigns (he failed to win the nomination back in 2008), it also threatens to make it more difficult for him to connect with the average voter. That vulnerability was highlighted in December when Romney offered a $10,000 bet to then-candidate Rick Perry -- a sum many Americans could only dream about wagering (in fact, it's equal to a

fifth of the median U.S. household income)

.

So how have similarly wealthy American fared in politics? To put things in context, Wealth-X, a consultancy that specializes in research on ultra-high net worth individuals, compiled a ranking of the richest Americans to run for president in the past 20 years. As you'll see, being filthy rich isn't a roadblock to winning the nomination, but it doesn't seem to help you seal the deal in the general election.

Fifth-Richest: Al Gore ($100 million)

Al Gore and Romney have more in common than you might expect: Both are Harvard men, both are sons of prominent politicians and both have struggled with the perception that they are stiff and unable to connect with the average voter. But whereas Romney had made his fortune by the time he went into politics, it wasn't until Gore left office that he really started raking in the big bucks. (Wealth-X's list is based on current net worth, though Gore is the only member of the top five who made most of his wealth post-politics.)

In addition to the hefty speaking fees accorded to most prominent former politicians, Gore also has a number of lucrative business interests. He has sat on the boards of

Google

and

Apple

, which earned him some sought-after stock options that made him

tens of millions of dollars

. He's also the founder of media company Current TV, and has put his money where his mouth is via stakes in investment firms that finance alternative energy companies.

Gore, of course, won the Democratic nod in 2000 but lost to George W. Bush, who may have had more money in the bank but still managed to cultivate a more populist image than Gore.

Fourth-Richest: John Kerry ($240 million)

Senator John Kerry's (D-Mass.) wealth is on par with Romney's, who also made his name in politics in the Bay State (and who also battles a reputation for political flip-flopping). But they made their money in different ways: While Romney earned cash hand-over-fist in the financial services sector, Kerry just married the right woman.

Most of Kerry's wealth comes from his marriage to Teresa Heinz, who made most of her money from her marriage to her first husband, Sen. John Heinz. And the ticket got even richer thanks to another lucrative marriage of sorts: Kerry chose as his running mate John Edwards, a fantastically successful trial lawyer with a current net worth of $45 million.

It's unclear how much of that wealth contributed to Kerry's elitist reputation, but it didn't help him win the presidency: Bush, facing a much richer opponent than the previous one, nevertheless triumphed once again.

Third-Richest: Mitt Romney ($250 million)

While the Occupy Wall Street movement has faded from the headlines, it at least succeeded in starting a national dialogue about income inequality and tax rates. So we can't help but wonder if the current focus on Romney's tax rate and personal wealth -- earned in the financial services sector, a popular bogeyman for the movement -- is at least partly due to the lingering effects of that dialogue.

Of course, Romney isn't really helping matters. There was that ill-advised $10,000 wager, which Democrats quickly pounced on, starting

Mitts10kBet.com

and asking working Americans what they could do with that sort of money. There was his comment that "corporations are people, my friend" which fueled the perception that he's the candidate of Wall Street. And just last week he put his foot in his mouth again when he said that his speaking fees, which total more than $373,000, were "not very much."

So far it's unclear how much of a dent Romney's wealth has made in his campaign. A recent attempt by Republican rivals to besmirch his work at Bain Capital seemed to backfire on the other candidates. The general election, though, is another story. While some analysts say that President Obama will prove better at connecting with the struggles of working class Americans, polls suggest that the American people see Romney as perfectly able to

understand the problems of ordinary Americans."

If he does manage to win the presidency, Romney will be breaking the mold: At the risk of spoiling the rest of this article, we can tell you that none of the candidates in the top five were elected president.

Second-Richest: Steve Forbes ($450 million)

It's probably appropriate that Forbes makes this list, given that the magazine that bears his name is most famous for ranking the richest people in the world. And while Forbes doesn't quite make it into the billionaire rankings, he's certainly among the richest men ever to run for president.

Forbes, of course, made his money by inheriting his father's wealth and the family business, a publishing empire. He ran for president twice, both times as a Republican: In 1996 he won a couple of primaries but lost to Bob Dole, and in 2000 he never had much of a chance to begin with.

These days, Forbes' involvement in politics is largely limited to endorsing other Republican candidates. Prior to the South Carolina primary he spoke about his support of

Rick Perry

, though it looks like he bet on the wrong horse there.

The Richest: Ross Perot ($3.58 billion)

Perot, who ran for president in 1992 and 1996, is the only billionaire ever to shoot for the highest office in the land. (No, Donald Trump doesn't count, as he never officially threw his hat in the ring). Perot's also the only independent candidate to make the list, and he managed to grab close to 20% of the popular vote in 1992, making him one of the most successful third-party candidates ever.

A tech billionaire before tech billionaires were cool, Perot made his fortune by starting

Electronic Data Systems

back in the 1960s. And he put that money into running an unconventional campaign, buying up television time and regaling voters with charts and graphs outlining his economic philosophies.

Like the others on this list, he never made it to the Oval Office. Even so, perhaps Romney can look at Perot and take heart: While Perot didn't win, he managed to grab support from middle-class Americans from all walks of political life despite having more money than most people could ever dream of. Having an incredible fortune may make it difficult to claim a real connection with the working man, but it's not necessarily a deal-killer.

Matt Brownell is a staff reporter for MainStreet. You can reach him by email at matthew.brownell@thestreet.com, or follow him on Twitter @Brownellorama.