A sex scandal hasn't stopped Republican campaigns from digging up dirt on Democratic challengers to use in a barrage of negative ads scheduled to air just before the Nov. 7 election.

Not only is the National Republican Congressional Committee going ahead with its advertising strategy, but it is warning that Democrats now trying to take advantage of the charges against former Florida Rep. Mark Foley may be opening themselves up to tougher scrutiny.

Ed Patru, a spokesman for the NRCC, told FOXNews.com that Democrats who have tried to suggest that House GOP leaders were lax in their monitoring of Foley, could find themselves being questioned, perhaps about past votes on predator legislation or other child advocacy issues.

"In some cases, Democrats have overstepped on this and they are opening themselves up to attacks on their own records," Patru said in a phone interview.

About 90 percent of the NRCC's advertising budget in the last few weeks of the campaign will go to "contrast ads," Patru said, and opposition research teams have been dispatched to dig into the pasts of Democratic candidates in tight races.

"We've had over a year and a half to do our homework on the candidates that are running against our incumbent Republicans," Patru said. "Ultimately, every race will come down to a contrast between two candidates on a local ballot. To that end, we're going to paint a clear contrast."

Patru added that he's sure the strategy will go both ways ahead of the Nov. 7 election, in which Democrats need 15 seats to take the House majority, and six to win the Senate.

"Democrats are certainly running their share of contrast ads as well," Patru said. "No party has a monopoly on contrast ads. We just believe our research is more devastating than theirs, and that's a function of Democrats recruiting bad candidates."

But Democratic critics say the GOP strategy signals desperation, and it may be too late.

"The Republicans have concluded they have nothing positive to say about Bush's agenda," said Bob Mulholland, a California Democratic strategist with his own reputation as an opposition research specialist. "It's a sign of a desperate tactic. They are so worried about the Bush bird flu that they are trying to demonize their Democratic opposition."

Analysts say Republicans are particularly vulnerable this year, due to an anti-incumbent mood, combined with President George W. Bush's low approval ratings, tepid support for the war in Iraq and a pessimistic mood about the general direction the country is headed.

The challenges for the GOP have been compounded by Foley's resignation on Sept. 29 after he was questioned about lurid e-mails with a former teenage House page. Shortly afterward, sexually explicit instant messages with another House page were published. Since then, more pages have come forward and the attention has shifted from Foley's alleged personal escapades to the GOP House leadership's failure to act on the information they had about his behavior.

House Speaker Dennis Hastert and others have responded to criticisms by suggesting that the information on Foley was timed for release by Democrats to have the gravest impact on Republicans ahead of the election. No evidence has yet been uncovered that Foley's correspondences with the pages were given to reporters by Democratic sources.

"I don't know if it's the Democrats pulling this one out on the Republicans or not," said Terry Madonna, public affairs professor at Franklin & Marshall College in Pennsylvania.

Madonna said it is ironic that after spending so much capital on their own opposition research, Republicans would be blindsided by their own sex scandal. But, he said, Republicans' best laid plans to improve their chances at the polls through negative ads at the district level may be all for naught.

"I tell you, if [negative advertising] is working," he said, "I don't know where."

Congressman: Opposition Research a Must

Rep. Tom Cole, R-Okla., has been stressing the need for good opposition research about Democratic challengers. Just last month, he told Republican candidates to take advantage of opposition research immediately, if they haven't already, in order to "define your opponent immediately and unrelentingly."

"Do not let up -- keep the tough ads running right up to Election Day," Cole wrote in a memo to Republican colleagues. "Know your opponent's record and weaknesses inside out -- and exploit them."

Mark Montini, a campaign consultant who regularly farms out opposition research for his mostly Republican clients and runs an online service called CampaignSecrets.com, says this year's midterm election is so critical, and at least 30 to 40 races are so close, that Republicans couldn't possibly be alone in engaging in opposition research and attack ads.

"Everybody knows this is a big midterm election … at stake is the majority in both houses," said Montini. "It's not a sign of desperation at all. This is everybody trying to find another 100 or 200 votes. If the campaigns tell you they are not doing this, they are lying."

Already, ads highlighting Republican opposition research are on the air, and they are not sparing in their criticism.

For instance, Republicans have advertised that Joe Donnelly, a Democrat challenging Republican Rep. Chris Chocola in a pure toss-up race in Indiana, was delinquent on his taxes 15 times.

In Colorado, a 527 group called "Coloradoans for Justice," which has been linked to prominent state Republicans, is running an ad against Democratic gubernatorial candidate Jim Ritter.

The ad accuses then-District Attorney Ritter of plea bargaining with a drug-addicted hit and run driver who killed a 4-year-old girl in 2000. It features the family of the victim expressing anger at the offender's light eight-month sentence, as portrayed in the ad.

It is "one of the most powerful political attack ads I've seen in years," said CBS4 Denver reporter Raj Chohan.

But what the ad doesn't say, according to Chohan, is that the woman served more than four years including residential treatment, and the evidence may not have been strong enough to take the case to court and win.

Though the GOP ads may be withering, they aren't the only ones rippling though the airwaves.

Virginia Sen. George Allen has faced allegations that he used "the n-word" in college. That charge came on top of accusations that Allen knew he was making a racial slur when he called an Indian-American videographer working for his opponent a "macaca," a racial slur used in North Africa against darker-skinned Africans.

On the flip side, Allen opponent Jim Webb has been blasted by the senator for a 1978 paper he wrote condemning women in military combat and in the U.S Naval Academy.

Even Kinky Friedman, the colorful libertarian running for governor of Texas, has had to answer for past remarks after he too was heard uttering the “n-word” on a 26-year-old audiotape of a standup routine he did in Houston. Friedman's campaign has responded that the musician, mystery novelist and animal rights advocate has tried to expose and lampoon racism in his songs and comedy acts.

"A lot of these campaigns have gotten really raunchy," Madonna said, blaming both parties. "I've never seen any evidence that one party is overwhelmingly more guilty than the other."

Opposition Research is an Old Strategy Getting Costlier

Opposition research -- or as some call it, muckraking -- is nothing new, though the fee for expert dirt-diggers and the dissemination of potentially explosive material has gotten more expensive and sophisticated in recent years.

"It's one of the big growth industries in campaigns -- private detectives of the campaign world," Madonna said.

Montini said the cost of an opposition research "package" typically depends on the required amount of digging. "If you have a challenger who has been involved in a Fortune 500 business and politics for 50 years, $20,000 might not get you through the last decade," he said.

On the other hand, "If your challenger had been a community volunteer and a school teacher over the last decade, you are going to find it hard to spend $2,000," Montini said. In this year's average closely-contested House race, where a vulnerable incumbent faces an experienced and tough challenger, "I think $20,000 is on the low side," he said.

Once the goods are delivered to the campaign, it's anyone's guess where it goes. Montini suggested that no more than 5 percent of the information uncovered through opposition research is actually used against an opponent.

When it is used, campaigns sometimes spread the information directly. However, Montini said they need to do it wisely, so that the candidate throwing the dirt doesn't look mean or petty.

"Unanticipated consequences in politics are always a problem," added Madonna. "Intervening events often cause campaigns and election cycles to go off foot."

More often than not, information will find its way to reporters, or other third parties, like political action committees, that tend to be interested in publicizing the dirt. Free from typical financial reporting restrictions are Web logs or 527 groups, named after their Internal Revenue Service status. All are effective fronts for partisan activists.

"That's a pretty common practice now," Madonna said of third party activities.

Patru insists that the committee's investment into opposition research and subsequent advertising isn't as tawdry as critics contend, plus it's paying off.

"They're absolutely effective," he said. "We don’t run ads that don't move numbers."