Republicans are pouring cash into House districts that voted for President Biden by as much as 20 points, targeting under-the-radar battlegrounds amid growing signs of a red wave.

Why it matters: Infusions of funding by both parties into these solidly blue seats signal the potential for a Republican landslide, further complicating the Democratic calculus on which races to defend.

Context: These districts are bluer than Washington state, which backed Biden by 19 points in 2020.

Driving the news: The National Republican Congressional Committee is making three six-figure investments in districts that went for Biden by 20 points in 2020, a source familiar with the matter tells Axios.

• California's 26th: Rep. Julia Brownley (D) is sounding the alarm to colleagues about her surprisingly competitive race against Republican Matt Jacobs as Republicans make inroads in other West Coast blue states.
• New York's 25th: Rep. Joe Morelle (D) faces former Rochester police chief La’Ron Singletary — who garnered headlines in 2020 when he was fired after the death of a man in police custody — as crime has emerged as a top issue up and down the ballot in New York.
• Pennsylvania's 12th: Progressive Democrat Summer Lee is running in this Pittsburgh-based district to replace Rep. Mike Doyle (D-Pa.) — against a Republican local legislator also named Mike Doyle.

The other side: Democrats have been investing in these races as well amid signs of their competitiveness.

• Democratic Congressional Campaign Committee spokesperson Tommy Garcia told Axios. "The DCCC has already invested in these seats that are critical to maintaining the majority."
• "The NRCC and [chairperson] Tom Emmer can chase windmills all day long while their endangered incumbents struggle — but the DCCC along with outside spenders will make sure Matt Jacobs, La'Ron Singletary, and Mike Doyle never see the halls of Congress."

The big picture: Investments in these races go beyond just the party committees.

• House Speaker Nancy Pelosi (D-Calif.) has transferred $2,000 to Morelle, as has Majority Leader Steny Hoyer (D-Md.), while House Minority Leader Kevin McCarthy (R-Calif.) has given $5,000 to Singletary.
• Pelosi has also given $2,000 to Summer Lee.

The intrigue: The name confusion in Pennsylvania's 12th has led at least some Democratic voters to mistakenly vote by mail against Lee, according to her campaign manager Abigail Gardner.

• “It’s come up, but it’s not every voter,” Gardner told Axios. "It’s a lot of older folks who are just used to voting for [Rep. Doyle] and think maybe he switched parties." She said that it was more of an issue when mail-in ballots were first sent out.
• “Overwhelmingly our conversations are people who thought Summer was running unopposed,” she added.
• Lee's campaign has been working hard to clear up the confusion, running ads and sending texts differentiating between the two Doyles. A pro-Lee ad from Justice Democrats also focuses on the name confusion.

Yes, but: The name confusion is not the only factor at play in the race.

• Lee’s left-wing politics have made her a foil for Republicans elsewhere in the state. In the neighboring 17th District, Republicans are running an ad tying Democrat Chris Deluzio to Lee and Rep. Alexandria Ocasio-Cortez (D-N.Y.).
• And Rep. Doyle, who endorsed Lee's more moderate rival over her in the Democratic primary, said during a press conference to address the name confusion, "I support all the Democrats running on the ticket," without naming Lee specifically.

Go deeper: Other unlikely battlegrounds are suddenly popping up on both parties' radar screens. House Majority PAC spent a whopping $2.3 million this week to help Rep. Josh Gottheimer (D-N.J.), a moderate representing a district Biden carried by 12 points.

• VoteVets, another big-spending Democratic outside group, spent $2 million this week boosting Rep. Mikie Sherrill's (D-N.J.) standing. Sherrill, whose north Jersey district backed Biden by 17 points, isn't even on the Cook Political Report's list of potentially vulnerable lawmakers.
• Both parties are now pouring millions into DCCC chair Sean Patrick Maloney's Hudson Valley district (Biden +10), as Republicans bet big for a powerful symbolic victory.

Reality check: Even as some of these deep-blue districts are looking surprisingly competitive, Democrats are still holding their own in some traditional battleground districts. A series of four NYT/Siena House race polls — in Kansas, Nevada, New Mexico and Pennsylvania swing seats — still show all four Democratic candidates ahead or tied.