VERONA, N.Y. — Pushing further into Republican territory one week before Election Day, Democrats are poised to expand their majority in the House while Republicans, weighed down by President Trump’s low standing in crucial battlegrounds, are scrambling to offset losses.
Bolstered by an enormous cash-on-hand advantage, a series of critical Republican recruitment failures and a wave of liberal enthusiasm, Democrats have fortified their grip on hard-fought seats won in 2018 that allowed them to seize control of the House. They have trained their firepower and huge campaign coffers on once-solid Republican footholds in affluent suburban districts, where many voters have become disillusioned with Mr. Trump.
That has left Republicans, who started the cycle hoping to retake the House by clawing back a number of the competitive districts they lost to Democrats in 2018, straining to meet a bleaker goal: limiting the reach of another Democratic sweep by winning largely rural, white working-class districts like this one in central New York where Mr. Trump is still popular. Depending on how successful those efforts are, Republican strategists, citing a national environment that has turned against them, privately forecast losing anywhere from a handful of seats to as many as 20.
That is starkly at odds with Mr. Trump’s own prediction just days ago that Republicans would win back control of the House, which Speaker Nancy Pelosi declared “delusional,” echoing the private assessments of many in the president’s own party.
“The Democrats’ green wave in 2018 has turned into a green tsunami in 2020, which combined with ongoing struggles with college-educated suburban voters, makes for an extremely challenging environment,” said Corry Bliss, a Republican strategist who helped lead the party’s failed effort in 2018 to protect its House majority, referring to the torrent of Democratic campaign cash. “There are about a dozen 50-50 races across the country, and the most important factor in each is if the president can close strong in the final stretch.”
The terrain for House Republicans was not supposed to be this grim. But Mr. Trump’s stumbling response to the pandemic and inflammatory brand of politics have alienated critical segments of the electorate, particularly suburban voters and women, dragging down congressional Republicans and opening inroads for Democrats in districts that once would have been unfathomable.
“I don’t think too many people would have thought that at the beginning of this cycle, but we are playing deep into Trump country,” Representative Cheri Bustos of Illinois, the chairwoman of House Democrats’ campaign arm, said, noting that “a third of a billion dollars” and strong recruits had yielded “a good secret sauce.”
Eyeing new opportunities in districts that have traditionally been conservative strongholds, Democrats have charged into suburbs across the country. In the Midwest, they are targeting Representatives Don Bacon of Nebraska, Ann Wagner of Missouri, and Rodney Davis of Illinois. They are also storming once ruby-red parts of Texas, positioning themselves in striking distance of picking up as many as five seats on the outskirts of Houston and Dallas.
Perhaps nowhere is the dynamic on starker display than outside Indianapolis, in a sea horse-shaped district held by Representative Susan W. Brooks, Republican of Indiana, who is retiring. The district, one of the state’s wealthiest and most educated, has been reliably conservative, sending Republicans to the House since the early 1990s and supporting Mr. Trump in 2016 by eight points.
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But this year, Democrats view the district as one of their best opportunities to flip a seat, betting that distaste for Mr. Trump will buoy support for their candidate, Christina Hale, a former member of the Indiana General Assembly who boasts of having worked to pass legislation with Vice President Mike Pence when he was the state’s governor.
“People here are just so fatigued of all the drama and the constant news cycle,” Ms. Hale said in an interview. “They’re just really looking for practical, competent, empathetic people to represent them in Washington and people that will collaborate across the aisle.”
Two years ago, armed with similar brands and messages, Democrats won 31 districts where Mr. Trump had prevailed in 2016. Most of them are expected to cruise to re-election, capitalizing on their huge fund-raising hauls and weak Republican challengers.
If Republicans have any reason for optimism, it is in largely rural areas like New York’s 22nd District, populated by mostly white voters who still strongly support the president. They are bullish about their chances in this race, where Claudia Tenney is seeking to reclaim her seat from Representative Anthony Brindisi, the Democrat who ousted her in 2018 after winning by fewer than 4,500 votes.
While Ms. Tenney described herself in an interview as independent, her campaign is gambling that Mr. Trump’s presence on the ballot this year could help her edge past Mr. Brindisi on Election Day. All through the district, along roads that wind through farmland and tucked among elaborate Halloween displays, yard signs paid for by the Tenney campaign blare, in all capital letters, “Trump Tenney” — a clear indication of how their fortunes are intertwined. (Mr. Trump on Tuesday also tweeted in support of Ms. Tenney.)
“I just find it really hard to believe that he’s not going to win this district by double digits, and I think his policies have done really well for our region,” Ms. Tenney said of Mr. Trump. “They would rather have a president and a leader who’s going to stand up for them than get hung up on personality issues.”
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But Mr. Brindisi, who has sought to build a platform rooted in health care and local constituency work and legislation, argued that Ms. Tenney lost in 2018 because she had failed to deliver on her promises to the district.
“People don’t want to turn back the clock. They want to continue to go forward,” Mr. Brindisi said. “At the end of the day, if I meet with people on the street in this district, what they’ll tell me is, ‘Anthony, I don’t care if you’re a Democrat or Republican, just get things done.’”
Elsewhere around the country, some challengers whom Republicans had promoted as strong recruits, like Nancy Mace, the first woman to graduate from the Citadel who is running against Representative Joe Cunningham of South Carolina, have found themselves stunted by a dismal national environment and unable to get their attacks against centrist lawmakers to stick.
“When you try and paint somebody that’s clearly a moderate as super extreme, I just don’t think it works,” said A.J. Lenar, a Democratic ad maker and strategist who works with Mr. Cunningham and cut an ad poking fun at attempts to brand him a socialist.
Making matters worse for Republicans is the state of their fund-raising. Democrats in the most competitive races are sitting on a 5-to-1 cash-on-hand advantage over their Republican challengers, and Democratic candidates overall were poised to spend nearly twice as much on television ads from Labor Day to Election Day, according to strategists tracking the buys. In New York, Democrats are outspending Republicans by $9 million on television in support of Representative Max Rose, who holds a Staten Island seat that Republicans believe is one of their best opportunities.
Some Republican candidates, including Ms. Tenney, were out-raised so handily that outside groups, like the Congressional Leadership Fund, a House Republican super PAC, have been forced to step in to carry out campaign fundamentals like advertising and phone calls, as well as get-out-the-vote programs. Ms. Tenney is among a group of Republican candidates this cycle who have run almost no ads themselves, leaving the super PAC to carry their entire television campaign.
Democrats’ giant cash advantage also means they can afford to play in longer-shot races in Alaska and Montana, forcing Republicans to sink millions into those at-large seats in an effort to build a firewall against a potential wave.
Even though his party appeared to be playing more defense than offense, Representative Tom Emmer of Minnesota, the chairman of the National Republican Campaign Committee, argued in an interview that Republicans could still take back the House. Democrats in districts like New York’s 22nd, which Mr. Brindisi flipped two years ago, appear to be on stronger footing than they actually are, he said, because of national polls that undercount conservatives — an assertion few of his peers share.
But he acknowledged his prediction assumed Mr. Trump was as popular with voters in those districts as he was four years ago.
“It really depends on if the president performs at or near 2016 levels,” Mr. Emmer said. “If not, it becomes a lot more difficult.”
That is also the challenge for Victoria Spartz, the Republican state senator who is running against Ms. Hale in the suburbs of Indiana, where internal polls show support for Mr. Trump eroding. She has used her rags-to-riches story of emigrating from the Soviet Ukraine to emphasize her strong belief in limited government.
But Ms. Spartz is facing the same headwinds buffeting her party in districts around the nation. After prevailing in a crowded primary by flaunting her conservative credentials, she must now convince voters of her independence from Mr. Trump and Republicans.
“I wish people would pay more attention and actually vote for the candidate,” she said in an interview, “not for the party.”
Emily Cochrane reported from Verona, N.Y., and Catie Edmondson from Washington. Luke Broadwater contributed reporting from Washington.