WASHINGTON — Mitt Romney says he "saw" his father "march" with Martin Luther King Jr. Rudolph Giuliani claims that he is one of the "five best known Americans" in the world. According to John McCain, the Constitution established the United States as a "Christian nation." Ron Paul believes that a "NAFTA superhighway" is being planned to link Mexico with Canada and undermine U.S. sovereignty.

On the other side of the political divide, Sen. Barack Obama says there are more young black males in prison than in college. Sen. Hillary Clinton claims she has a "definitive timetable" for withdrawing U.S. troops from Iraq. John Edwards insists that NAFTA — the North American Free Trade Agreement — has cost Americans "millions of jobs." Sen. Joe Biden boasts about his experience negotiating an arms control treaty with Leonid Brezhnev.

All those claims, made over the last four months as part of the presidential campaign, are demonstrably false.

With just four days to the Iowa caucus, the art of embellishment and downright fibbing is alive and well in American politics. But the popularity of blogs, YouTube and information databases like Lexis-Nexis, along with the 24-hour news cycle, has made it easier than ever for the media and rival campaigns to spot the mistakes and exaggerations of presidential candidates.

"The rules of the game are changing," said Kathleen Hall Jamieson, a University of Pennsylvania professor and veteran observer of political campaigns. "A claim that something is inaccurate is being vetted more quickly and moving into the media more quickly."

On Friday, when former Arkansas governor Mike Huckabee attempted to link the chaotic situation in Pakistan following the assassination of Benazir Bhutto with the issue of illegal immigration, skeptical reporters immediately questioned the claim. The Huckabee campaign was unable to provide convincing backup for his assertion that "we have more Pakistani illegals coming across our border than all other nationalities except those immediately south of the border," an assertion at odds with U.S. Border Patrol data.

Huckabee later cited a March 2006 Denver Post article to support his claim that 660 Pakistanis crossed U.S. borders illegally last year. In fact, the newspaper wrote that 660 Pakistanis were apprehended crossing into the U.S. between 2002 and 2005. U.S. Border Patrol data show that Canada, Philippines, and Poland accounted for larger numbers of illegal immigrants than Pakistan.