Click here to watch "Dos Caras."

John McCain has been catching a lot of heat for several of his recent TV ads, with even the likes of Karl Rove acknowledging that the McCain spots don't always pass the truth test. But Barack Obama has launched some controversial ads of his own recently, including "Dos Caras" (subscription), a new Spanish-language spot -- running in Colorado, New Mexico and Nevada, with plans for a buy in Florida -- that links McCain to radio talk show host Rush Limbaugh's rhetoric.

Flashing quotes from Limbaugh on screen -- "...stupid and unskilled Mexicans" and "you shut your mouth or you get out" -- an announcer laments that Republicans have "made" Latinos "feel marginalized in this country we love so much." He then goes on to accuse McCain and the GOP of having "two faces" when it comes to immigration policy: "One that tells lies just to get our vote. And another, even worse, that continues the failed policies of George Bush that put special interests ahead of working families."

But as ABC's Jake Tapper points out, Limbaugh's quotes are taken out of context in the spot. Moreover, McCain and Limbaugh have hardly been of one mind when it comes to immigration policy. The conservative talk show host lambasted the bill the Arizona senator put forth earlier this year and was one of McCain's most vociferous critics during the Republican primary race.

There's no doubt that the tone of advertising coming out of both the presidential candidates' camps has taken a negative turn over the past several weeks. Contrary to what most talking heads have been suggesting, however, Obama and not McCain ran a larger percentage of attack ads in the week following the Republican National Convention, according to a new study [PDF] from the Wisconsin Ad Project. Whereas 56 percent of McCain's spots could be characterized as negative, according to the report, over three-fourths of Obama's ads had some not-so-nice things to say about his rival.

Sarah Niebler of the Wisconsin Ad Project said that this is the first week the group has examined in which Obama has outpaced McCain in attack ads. "Ultimately we think this campaign is about Obama. People know a lot about McCain... so it seems more likely that as the campaign continues, Obama will run ads about Obama. McCain will also run ads about Obama. But this week, for whatever strategic reason... there was a shift," she explained.