Facts are stubborn things, but they often meet their match with politicians.
Campaigning in Pennsylvania, Tuesday, Sen. Hillary Clinton, D-N.Y., continued to argue she has opposed the North American Free Trade Agreement since 1992.
"I did speak out and opposed NAFTA," Clinton told an AFL-CIO audience in Philadelphia. "I raised a big yellow caution flag. I said, 'I'm not sure this is going to work.'"
But if Clinton "spoke out" against NAFTA, she did so quietly and behind closed doors, and made no mention of it in her 2003 autobiography "Living History."
Fact Check: Clinton's Anti-NAFTA Rhetoric
In fact, Clinton worked to sell NAFTA at a Nov. 10, 1993, meeting with business women detailed in her recently-released White House schedules.
Three attendees of that closed-door briefing told ABC News last month that Clinton's comments were supportive of the trade deal eventually signed into law by her husband.
Laura E. Jones, executive director of the United States Association of Importers of Textiles and Apparel, who was there, said, "There was no question that everyone who spoke, including the first lady, was for NAFTA. It was a rally on behalf of NAFTA to help it get passed. It's unquestionable. And there are many people out there who were there, who remember the incident, who work in this industry."
Julia K. Hughes, senior vice president of the same organization, is likewise incredulous of the Clinton campaign's claims.
"This is such a non issue to us, because, obviously, it was a pro-NAFTA group and a pro-NAFTA event," said Hughes. "It was a 100 percent pro-NAFTA event. No one suggested any inklings of doubt, since part of the agenda was to promote enthusiasm for passage of NAFTA."
Did that include then-first lady Clinton?
"Absolutely. She was the highlight of the event. She was absolutely the capper to the event. It was a positive rally. I assure you, if there had even been a hint of waffling from her — because we were in the last days before NAFTA passed, and it was a pretty hectic time — we would have freaked out."
"It wasn't a drop-by — it was organized around her participation," said one attendee. "Her remarks were totally pro-NAFTA and what a good thing it would be for the economy. There was no equivocation for her support for NAFTA at the time. Folks were pleased that she came by. If this is still a question about what was Hillary's position when she was first lady, she was totally supportive of NAFTA."
A second attendee recalled, "They were looking for women in international trade who supported NAFTA. Sen. Clinton came by at the end. And, of course, she asked for our support and help in passing NAFTA."
Claiming Credit for Children's Health Insurance Bill
In another instance of campaign rhetoric not matching the facts, when Clinton talks about health care reform on the campaign trail, she claims credit for the multibillion-dollar children's health insurance program S-CHIP as one of her signature accomplishments.
Enacted in 1997, the program has provided $24 billion over 10 years to states to cover more than 6 million children whose families cannot afford private insurance, but who earn too much to be eligible for Medicaid.
A Clinton campaign TV ad says she "got health insurance for 6 million kids."
As first lady, Clinton did help by pushing her husband, former President Bill Clinton, to support the program. However, the bill was written and the charge led by Sens. Ted Kennedy, D-Mass., and Orrin Hatch, R-Utah.
"Where I think she has gone too far is when she drops the qualifier, and she says, 'I created S-CHIP,' and in that case, that's not true," Bill Adair of Politifact.com said.
Obama's Oil Slick
However, Clinton isn't the only Democratic candidate making dubious claims on the campaign trail.
In a new TV ad about gas prices, Sen. Barack Obama, D-Ill., says: "I don't take money from oil companies."
While it's true that Obama doesn't take donations from the oil companies' political action committees, he has taken $213,884 from people in the oil and gas industry, much of it raised by two oil company CEOs, according to the nonpartisan Center for Responsive Politics.
"I'm not quite sure why a bunch of individuals, who are executives at oil companies, giving the limit, which may add up to $30,40,50,000, would be less significant and less potentially influential on the candidate than PAC money," Viveca Novak of Factcheck.org said.
Obama avoids credit for answers in a 1996 questionnaire supporting a complete ban on handguns and taking other liberal positions he now says he never held.
The Obama campaign blames the answers on a staffer and says the senator "never saw or approved" the questionnaire.
However, in a copy of that questionnaire obtained by ABC News, Obama took notes on it — calling into question the claim he "never saw" it.
ABC News' Avery Miller contributed to this report.