WASHINGTON (AP) — Forget kissing babies on the campaign trail. The millions of dollars' worth of political advertisements airing before the early primary elections are turning out to be money well spent: The ads have affected primary results more than other forms of campaigning, including personal appearances by candidates, campaign speeches or town hall meetings, according to an analysis by The Associated Press.

The AP's study of advertising purchases, campaign stops and demographic data offers the first tangible signs of how new super political action committees, which can spend unlimited amounts of cash to influence elections, are poised to remake presidential politics this year. So far, those groups have paid for at least $10 million in ads — and GOP voters haven't even decided whom they want to challenge President Barack Obama for the White House.

The ad frenzy already has taken hold in South Carolina, the site of the next Republican primary on Saturday. In the weeks leading into the contest, campaigns and super PACs have spent millions hammering their opponents. Last week, the Rick Santorum-leaning Red, White and Blue Fund said it was sinking an additional $600,000 in ads statewide; other groups supporting former Massachusetts Gov. Mitt Romney and Texas Gov. Rick Perry also have reserved airtime.

Recent data from New Hampshire and the Iowa caucuses show just how much influence ads have on voters. Texas Rep. Ron Paul and a super PAC supporting former Utah Gov. Jon Huntsman each had about $1.7 million worth of ads in their favor in New Hampshire. Paul and Huntsman respectively placed No. 2 and No. 3 in the state's primary, behind Romney. That's even as Huntsman made the most stops of any candidate in the state. He dropped out of the race Monday.

New Hampshire long has been a place where voters pride themselves on so-called retail politics, where candidates meet voters one-on-one across the state. But the super PACs' growing presence on the airwaves could be threatening that old-fashioned style of campaigning.

Marty Kaplan, a political communications expert at the University of Southern California, said campaigns have found for decades that the more negative they go, the higher they drive up the negative perception of their opponents. "If it wasn't working, they'd do something else," he said.

The AP's examination, which looked at official election results, Nielsen data and Census Bureau estimates, found that ad spending correlated more with election results than other known factors, such as a town's political party makeup and how often a candidate came to visit. Although other less-measurable dynamics may come into play — like a candidate's personal likability or voters' unforeseen reaction to his past — Kaplan said the AP's findings are in line with academic studies.

Take Concord, N.H., where Paul made half as many campaign stops as Rick Santorum in recent months. Paul, however, received 23 percent of the vote there compared with Santorum's 9 percent. Paul outspent Santorum about 70 times on ads across the state, with Santorum spending just $22,000.

Candidates and outside groups have spent not only mountains of cash on television; they've also hit their opponents with direct-mail leaflets and Internet ads. The Newt Gingrich-supporting Winning Our Future PAC — bolstered earlier this month by a $5 million donation from casino mogul Sheldon Adelson — recently disseminated a 28-minute Web movie and shorter TV spots slamming Romney for his record at a private equity firm.

But as the South Carolina voting nears, the ad campaigns risk backfiring. Robert Driggers, a computer engineer in Summerville, S.C., said he's so turned off by ads that he and his wife sometimes leave the room when they come on. "I've learned that the opposition running those ads are the ones to watch out for," he said, growing suspicious of their motives.

For now, the opposite has proved true. Roughly three-quarters of New Hampshire voters said campaign advertising was a factor in helping them decide whom to support, according to an exit poll conducted for the AP by Edison Research. A majority of Iowa caucus voters shared similar sentiments.

Perhaps fewer cases this election have proved to be more damaging than that of Gingrich, who was assailed by ads from the Romney-leaning Restore Our Future super PAC. Political operatives largely have cited the group's critical ads in Iowa for the former House speaker's poor showing in the state's caucuses. Gingrich finished fourth in the contest, behind Romney, Santorum and Paul.

The heavy influence of super PACs comes amid a handful of federal court cases, including the Supreme Court's Citizens United ruling in 2010, that stripped away some limits on campaign contributions. The new super PACs can't coordinate directly with campaigns, but many that are active in this election are staffed by longtime supporters or former aides of the candidates.

Many of the groups' donors will remain secret until Jan. 31, when some of the super PACs are required to report their finances to the Federal Election Commission.