WASHINGTON - An air war between Democrats and Republicans in upstate New York is giving a glimpse of attacks likely to be replicated in key congressional races in states including Pennsylvania and Iowa in the final three weeks of the campaign.

Democrats believe they can pin Republican candidates with presidential nominee Donald Trump’s now-infamous recorded remarks about groping women - even if GOP candidates have denounced the comments.

And that’s giving Democrats hope of what seemed impossible just a few weeks ago -- picking up enough seats to win control of the U.S. House of Representatives.

“As leading members of the GOP part ways with Trump on principal, one career politician doesn’t have the courage to take a position,” says a video posted to Democratic candidate Zephyr Teachout’s Facebook page.

Teachout is in a closely-watched race for New York's 19th District, called a “toss up” by the Cook Political Report, against Republican John Faso. Her ad shows Faso urging Republicans to unite behind Trump.

The video then flashes Faso’s quote in the New York Times: “I’m not saying I’ll vote for him. I’m not saying I won’t vote for him."

In the Syracuse area, television viewers are seeing an ad placed by the Democratic Congressional Campaign Committee on behalf of Colleen Deacon, running against Republican Rep. John Katko.

“In an unsettled world, Donald Trump and John Katko’s approach takes us down a dangerous path,” it says.

Similar commercials are beginning to appear in California, Minnesota, Michigan, New York, Pennsylvania and Wisconsin.

More are coming, said Bryan Lesswing, a spokesman for the Democratic committee.

“Over the next four weeks, we will hold Republicans accountable to their ugly standard bearer, and we’re confident that voters will do the same on Election Day,” he said in an e-mail.

In recent ads Republicans are also hoping to capitalize on the unpopularity of the opposition presidential candidate - Democrat Hillary Clinton. They're touting GOP candidates as a check on a candidate who may become president despite low marks with voters

An NBC News/Wall Street Journal poll found only 40 percent of those surveyed have a very or somewhat positive view of Clinton. Fifty percent had a negative view.

In another upstate New York district with a close-watched race for Congress, television viewers in the Poughkeepsie area see an image of Democrat Kim Myers pasted next to those of Clinton and House Minority Leader Nancy Pelosi. There’s an image of marching troops, then an “Out of Business” sign.

“ISIS is on the move. American jobs are disappearing,” says the ad placed by the National Republican Congressional Committee, “while Hillary Clinton and Nancy Pelosi seek rubber-stamps like Kim Myers to fast track their agenda.”

Another ad by the Republican committee says, “Extreme liberal Kim Myers supports Obamacare.”

Her Republican opponent, New York Assemblywoman Claudia Tenney, would “stand up” to Clinton, the ads say.

“Democrats are only offering the same failed liberal policies, liberal candidates,” said Katie Martin, a spokeswoman for the committee, in an interview about the line of attack.

Democrats face a tough climb as they try to gain 30 seats to take over the House. They are now outnumbered by Republicans, 246 to 186, with three vacancies.

Behind Democrats' optimism is an NBC News/Wall Street Journal poll taken after the "Access Hollywood" video of Trump surfaced. Forty-eight percent of voters said they want a Democrat-controlled Congress, while 42 percent want Republicans in charge.

A Fox News poll last week also found voters back Democratic congressional candidates, 48 to 42 percent.

Illustrating the importance of the House races, the Congressional Leadership Fund, associated with Republican House leaders, announced Friday that it is pumping $10 million into key races. Clinton’s campaign on Monday said it’s shifting $2.5 million each into Democratic House and Senate campaign organizations.

In addition, the Washington Post reported that internal Democratic polls show Republican candidates in a no-win situation over Trump. They will lose by cutting ties, but they also lose support if they remain loyal to him.

In many cases, Democratic ads are targeting Republicans who are seemingly caught in the middle - denouncing Trump’s comments but refusing to say whether they will vote for him.

Katko, for instance, has said he does not endorse either candidate. "They do not share my values," he said in a statement.

His campaign attorneys sent cease-and-desist orders demanding that Syracuse television stations stop running the ads, according to local news reports, saying their assertions that Katko supports Trump are not true.

In Pennsylvania, Republican State Sen. Lloyd Smucker, who is running in another closely contested race, has “strongly denounced” Trump’s comments as “lewd, inappropriate and appalling.”

However, Smucker, who is running for the congressional seat in the Lancaster area left vacant by retiring Republican Rep. Joe Pitts, has not gone so far as to say he will not vote for Trump, leaving him open to an ad being run by his Democratic opponent, Christina Hartman.

The ad shows the infamous video of Trump getting off a bus with former "Access Hollywood" host Billy Bush, then plays a portion of Trump's remarks about women.

“Is this our next president?” the narrator asks. “Well, Lloyd Smucker thinks so."

Republicans say internal polling in key House races hasn’t seen a change since the controversial recording was first reported by the Washington Post.

Thus far, Trump’s decline in the polls doesn't seem to be hurting Republicans in key Senate races.

Cook Political Report analyst David Wasserman, questioned in a blog post Friday whether the tactic will work in House races.

Many of those abandoning Trump over the recording are college educated, white Republicans - particularly women.

“But these suburban-dwellers are also the voters likeliest to stick with Republicans down ballot,” Wasserman said.

The highly followed newsletter still expects Democrats to gain between 10 to 20 House seats, particularly if Republicans discouraged by controversy over Trump decide not to vote.

But with only 37 races considered competitive in the country, the prospect of Democrats gaining 30 seats to win a majority “is still a reach,” he wrote.

Kery Murakami is the Washington, D.C. reporter for CNHI's newspapers and websites. Contact him at kmurakami@cnhi.com.