These organizations range from the newly created BornAliveTruth.org, an anti-abortion group that assails Obama's abortion votes, to MoveOn.org, the 10-year-old liberal organization that came to life during the impeachment of President Clinton.
In a patchwork of advertising, organizing and mailings, these groups are operating as independent militia forces for the campaigns and the national parties. By law, they cannot coordinate their efforts with the campaigns, but they take their cues from news events and from the ad strategies and messages that the campaigns themselves undertake.
"We'll see more of that type of activity because it is turning into a very close race where there a number of states that will be decided by a very close margin," said Anthony Corrado, a political scientist and an expert on political spending techniques at Colby College in Maine.
During the Democratic and Republican primary contests, McCain and Obama criticized outside groups, even those that came to their aid. But lately both campaigns have responded to their respective help with silence.
Despite new rules that make it easier for outside groups to be on the air at the height of the campaign, the amount spent so far is a small fraction of what independent groups had spent by this time in 2004. Several of the groups, particularly those that have emerged virtually overnight, need wealthy donors to sustain their campaigns. Only a few have come forth.
So far, the political left has relied on several established political action committees that raise money under strict limits from their donors. MoveOn, with nearly 4.2 million members, is putting its expanded membership muscle behind Obama with its largest ever voter and volunteer drive and with an up-to-$7 million fall advertising campaign, executive director Eli Pariser said.
"In last three weeks or so our membership has galvanized to a greater degree than in 2004," Pariser said.
Its first ad draws attention to the members of McCain's circle of advisers who have worked as lobbyists, particularly those who have had oil industry clients. "When it comes to gas prices, John McCain won't be taking care of you, he'll be taking care of 'My friends'...'My friends'...'My friends,"' the ad says as quick cutting clips show McCain addressing audiences with his usual salutation, "My friends."
MoveOn has seen a 1 million jump in its membership this year, Pariser said, approaching the size of the National Rifle Association. The organization has a goal of registering 500,000 young voters in battleground states. Pariser said MoveOn will share the data with other activist groups for efforts to get out the vote on behalf of Obama.
The Service Employees International Union on Sunday began spending $2 million in six battleground states, depicting McCain as out of touch on economic issues. And two Democratic-leaning political action committees - BraveNewPAC and Democracy for America - aired a modest, $50,000 three-day anti-McCain ad on CNN and MSNBC that features a former fellow prisoner of war criticizing the Arizona senator's temperament.
On the right, BornAliveTruth.org's $350,000 spot singles out Obama's efforts while in the Illinois Senate to defeat the Born Alive Infants Protection Act. Obama and abortion rights forces in Illinois have said the bill would have undermined the landmark Supreme Court case on abortion, Roe v. Wade. The ad will air during the next week in Ohio and New Mexico, especially targeting Albuquerque and Cleveland.
North Carolina-based RightChange.com plans to spend about $1.5 million criticizing Obama's tax plan in an ad that will run over the next two weeks on national cable networks, including Fox News Channel, CNN and CNN Headline News, said spokesman Tim Pittman.
RightChange.com and BornAliveTruth.org are nonprofit entities commonly known as 527s, for the section of the tax code that regulates them. Unlike political action groups, these organizations can raise money from individuals in unlimited amounts. The main donor of BornAliveTruth is Raymond Ruddy, a prominent anti-abortion philanthropist in Massachusetts who supported Mitt Romney for president in the GOP primary.
RightChange's main donor Fred Eshelman is a North Carolina pharmaceutical executive who has contributed more than $200,000 to Republican candidates and party organizations since 2002, according to Federal Election Commission records.
The efforts pale in comparison with what the campaigns themselves are spending, but they can be a distraction. Last month, a conservative group called the American Issues Project spent $2.9 million in an anti-Obama ad that questioned his association with former 1960s radical Bill Ayers. Obama was forced to respond, and targeted markets that ran the American Issues Project ad with twice as many commercials, according to Evan Tracey, whose firm tracks political advertising.
The American Issues Project ad was paid for by Harold Simmons, a McCain fundraiser who also helped finance the 2004 Swift Boat Veterans for Truth ads against then Democratic presidential nominee John Kerry.
Its organizers have said more ads may be coming.