Michele Bachmann has made more factual gaffes than any of the other Republican presidential candidates, according to PolitiFact.com, a nonpartisan Web site that vets public officials' statements.

Of the 35 Bachmann statements that PolitiFact.com had vetted as of Friday, only 14 percent were rated true or mostly true. Nine percent were rated half true, and 77 percent -- more than three-quarters -- were rated mostly false, false or pants on fire, a category reserved for assertions that are not only inaccurate but ridiculous, according to the editors of the Web site.

Bachmann, Perry Both Score Poor Regarding Gaffes, Inaccuracies

Rick Perry scored better than Bachmann, but still very poorly. PolitiFact.com vetted 81 statements by the Texas governor and found that 23 percent were true or mostly true, 27 percent were half true, and 49 percent were mostly false, false or pants on fire. Mitt Romney (48 percent true, 35 percent false) and Ron Paul (55 percent true, 23 percent false) had more respectable numbers, though by no means excellent.

Bachmann blames long hours on the campaign trail -- When you speak six times a day, slip-ups can occur, she said in August -- but even among her peers, she stands out. A 77 percent inaccuracy rating is nothing short of appalling.

Mistakes like her statement that Americans fear the rise of the Soviet Union, or her mixing up Elvis's birthday and death day, might be attributable to exhaustion. But other gaffes show a true lack of research and basic knowledge, not to mention shame. Here are five of the congresswoman's lowest moments.

1.  The HPV vaccine causes mental retardation.

At a Republican debate on Monday, Bachmann attacked Rick Perry for trying to require sixth-grade girls in Texas to get the Gardasil HPV vaccine, which protects against a virus that can lead to cervical cancer. But in a post-debate interview with Fox News, she went a step further than criticizing Perry for governmental overreach. There's a woman who came up crying to me tonight after the debate, she said. She said her daughter was given that vaccine. She told me her daughter suffered mental retardation as a result of that vaccine.

In reality, there is no evidence that the HPV vaccine has ever caused mental retardation, and Bachmann's false statement could have serious public-health consequences. It is already difficult for doctors to convince some parents that vaccines are safe -- which they are -- and careless remarks by public figures worsen the misperceptions surrounding life-saving vaccinations. (HPV is responsible for most cases of cervical cancer, which kills hundreds of thousands of women every year.)

Bachmann defended herself by saying she was merely repeating what the woman had told her, not endorsing it as scientific fact. But even many of her supporters criticized her, and rightly so: she had an obligation to check her facts before blindly repeating something that could harm public health.

2. The Founding Fathers worked tirelessly to end slavery.

In a speech in January, Bachmann praised the Founding Fathers for working tirelessly until slavery was no more in the United States. The problem is, while some of the Founding Fathers -- John Adams and Alexander Hamilton, for example -- criticized the institution of slavery, they did not work actively to end it. Others, like George Washington and Thomas Jefferson, even owned slaves themselves. In the Revolutionary War era, slavery was essentially a non-issue.

Bachmann stood by her statement, saying she was referring to John Quincy Adams -- John Adams's son and the sixth president of the United States, who was a child during the Revolutionary War. He did not enter politics in any capacity until 1794, when George Washington appointed him minister to the Netherlands, and he did not hold a major domestic position until he became a senator in 1803. Quincy Adams was not a Founding Father by any definition -- he did not sign the Declaration of Independence or the Articles of Confederation, help draft the Constitution or serve in any way as a leading figure in the founding of the United States, which is how Merriam-Webster defines the term. Bachmann insisted that he most certainly was a part of the Revolutionary War era. He was a young boy but he was actively involved. But helping his father with clerical work doesn't make him a Founding Father.

Let's say for the sake of argument, though, that Quincy Adams was a Founding Father. Then, yes, one of the Founding Fathers would have worked to end slavery, because Quincy Adams did become an abolitionist. But Bachmann's statement referred to the Founding Fathers, plural, implying that a large number of them fought against slavery -- and the reality is that, while some of them personally opposed slavery, they did not take serious action against it. Bachmann's claim is false by any measure, and it shows a simplistic, misinformed view of American history.

3. My husband and I never got a penny from farm subsidies.

Bachmann was accused of hypocrisy in June for opposing federal farm subsidies while she and her husband collected those very subsidies for their own farm. She deflected the criticism by saying, The farm is my father-in-law's farm. It's not my husband's and my farm. It's my father-in-law's farm, and my husband and I have never gotten a penny of money from the farm. But the financial disclosure forms that Bachmann herself filed with the clerk of the House of Representatives say she's gotten a lot more than pennies: between $15,000 and $50,000 a year in 2008 and 2009.

Once her claim had been disproven, Bachmann tried another tack, saying that she was listed as a trustee for purposes of succession but had not actually received any money from the farm. But campaign finance experts told PolitiFact.com that if that were the case, she wouldn't have had to report any income on her disclosure form -- she just would have had to disclose that she was a trustee. So all evidence points to Bachmann and her husband having benefited from the farm subsidies she decries, providing further proof that pork isn't pork when it's going to your district.  

4.  Standard & Poor's said the U.S. can't pay its debt.

In the aftermath of Standard & Poor's decision on Aug. 5 to downgrade the U.S. Government's credit rating, there was plenty of blame to go around. Bachmann blamed the fact that the debt ceiling was raised at all. I think we've just heard from Standard & Poor's, she said. When they dropped our credit rating, what they said is, we don't have an ability to repay our debt. That's what the final word was from them. I was proved right in my position. We should not have raised the debt ceiling. And instead, we should have cut government spending, which was not done.

This statement is incorrect in more than one way. First, Congress did cut government spending as a prerequisite for raising the debt ceiling -- not as much as Bachmann and many of her colleagues wanted, but $2 trillion is no pittance.

More substantively, though, Standard & Poor's explanation for downgrading the U.S.'s credit rating did not actually prove Bachmann right. The agency did note that the national debt was unsustainable in the long term, but it did not attribute the downgrade to the government's inability to pay its debts or to the decision to raise the debt ceiling. Quite the opposite, it attributed the downgrade to the partisan gridlock that prevented Congress from raising the debt ceiling sooner: The political brinksmanship of recent months highlights what we see as America's governance and policymaking becoming less stable, less effective and less predictable than what we previously believed, it wrote in an official report. The statutory debt ceiling and the threat of default have become political bargaining chips in the debate over fiscal policy.

If that wasn't clear enough, the director of Standard & Poor's, Joydeep Mukherji, told Politico that the agency was very concerned that people in the political arena were even talking about a potential default. That a country even has such voices, albeit a minority, is something notable. This kind of rhetoric is not common amongst AAA sovereigns. In other words, the U.S.'s credit rating wasn't downgraded because Congress raised the debt ceiling in spite of opposition from people like Bachmann -- it was downgraded because it came so close to not raising the debt ceiling thanks to people like Bachmann.

5FDR wrecked the economy with the Hoot-Smalley tariffs.

Back in 2009, Bachmann spoke on the House floor as part of a general Republican critique of President Obama's first 100 days in office. She talked about the small-government conservatism of Calvin Coolidge, who was president from 1923-1929, and then argued that the prosperity of the Roaring Twenties -- which ended with the stock market crash of 1929 and the beginning of the Great Depression -- was ruined by the big-government policies of Franklin D. Roosevelt. Specifically, she said the Hoot-Smalley tariffs turned a recession into a depression by overburdening businesses with high taxes.

First things first: there's no such thing as the Hoot-Smalley tariffs. It seems Bachmann was referring to the Smoot-Hawley tariffs, which were indeed passed during the Great Depression -- but not under Roosevelt. The tariffs were actually a Republican initiative through and through. They were proposed by Sen. Reed Smoot of Utah and Rep. Willis Hawley of Oregon, both Republicans, and then signed into law in 1930 by President Herbert Hoover, who was also a Republican.

Bachmann has every right to argue that the tariffs made a bad U.S. economy worse, but it wasn't the Democrats who did it. With this and her swine flu gaffe -- in which she claimed that the last swine flu outbreak happened under another Democratic president, Jimmy Carter, when it actually happened under Gerald Ford, a Republican -- Bachmann really needs to start double-checking who was president when before she says anything.