The ad for Democrat Steve Kagen says "politician Reid Ribble wants to phase out Social Security, forcing Wisconsin seniors to fend for themselves."

If you've been watching TV the past couple of weeks, you've probably seen a lot of grainy black-and-white photos of President Barack Obama, House Speaker Nancy Pelosi and your local congressional candidates.

Don't adjust your TV. The black-and-white photos -- which often depict the political leaders scowling, frowning or otherwise looking menacing -- are part of a biennial autumn ritual: the season of attacks.

It's at this point in the campaign that candidates go on the offensive. The political ads will get warm and fuzzy in the final days of the campaign, but for now, the candidates are highlighting the negatives about their opponents.

The fact-checking for our NPR-PolitiFact Message Machine feature has highlighted a couple of trends. Ads from Republican candidates and groups supporting the GOP often try to link Democratic candidates with Obama and Pelosi. The narrators of those ads speak in ominous tones as the unflattering images of Pelosi and Obama are shown. The Democrats" policies are labeled wasteful and "job-killing.”

Democratic ads rely on similar techniques, but instead of using Obama and Pelosi as the villains, they often focus on the Republicans" positions on Social Security, alleging that the GOP candidate wants to "privatize” or otherwise wipe out the retirement program.

Independent candidates are also on the attack. In Florida, Republican-turned-independent Charlie Crist is using the same techniques to go after his GOP opponent, Marco Rubio.

Here are a few attack ads that we've rated recently:

• In Ohio, the conservative anti-tax group Americans for Job Security attacked U.S. Rep. Zack Space, a Democrat, for supporting Pelosi and her "job-killing energy taxes, and her wasteful stimulus. And we still lost more than 2.5 million jobs." We rated that Half True.

• In a Wisconsin congressional race, Democrat Rep. Steve Kagen claimed that "politician Reid Ribble wants to phase out Social Security, forcing Wisconsin seniors to fend for themselves." But the ad is wrong in several ways:  Ribble is not a politician and has never run for office before. Plus, Ribble's comments about Social Security are taken out of context and twisted. PolitiFact Wisconsin gave this one our lowest rating, Pants on Fire.

• In the race for a Florida U.S. Senate seat, Crist alleged that Rubio tried to insert $1.5 million for a rowing institute into the Florida state budget. But it wasn't Rubio that sought that earmark, it was another lawmaker. PolitiFact Florida gave this one a Pants on Fire!

• Finally, PolitiFact Wisconsin examined a claim by a Milwaukee talk show host that an ad by U.S. Sen. Russ Feingold was a fake. The talk show host claimed that Feingold used a green screen to make it appear he was in front of his house. This one, too, earned a Pants on Fire.