The GOP campaign arm focused on House races is already dumping millions of dollars into swing districts, pushing for volunteers to be on the ground and door-knocking early as they try to save their majority.

Why it matters: In spite of former President Trump's alarm over absentee ballots in 2020, Republicans have come to terms with the national pivot toward early voting. And they're trying to limit what they view as a Democratic advantage there.

• "Election Day is no longer one day, it's 30 or 40 days in a lot of these states," one House Republican strategist told Axios.

Driving the news: The National Republican Congressional Committee is funding and standing up new field offices — which they call "battle stations" — in 21 GOP-held swing districts, according to a committee official.

• They anticipate spending eight figures on the effort, planning to launch additional sites in swing districts where Republicans are trying to go on offense.
• More than 1,000 volunteers are already involved and some offices have begun going door-to-door, with an overall goal of contacting five million swing voters before election day.

Zoom out: The map is not generous for House Republicans this year. A slim majority to start, New York's redistricting, a re-drawn Alabama seat and a string of vulnerable incumbents all make it more likely for Democrats to win back the majority this year.

• GOP officials recognize that many of their most vulnerable House districts are in solidly blue states like New York and California, which will not benefit from heavy investment by the national groups like the Republican National Committee in the presidential race.
• NRCC battle stations are trying to solve for that, helping campaigns get started on their ground game early, rather than waiting and saving resources for the final weeks of the election.
• "Republicans can beat Democrats on the ground this cycle with this unprecedented NRCC investment to persuade and turn out voters," NRCC Chairman Richard Hudson told Axios in a statement.

Zoom in: Of the 21 districts where battle stations have been set up, six are in California — for Reps. John Duarte, David Valadao, Mike Garcia, Ken Calvert, Michelle Steel and Young Kim.

• The list also includes five New Yorkers — Reps. Michael Lawler, Marc Molinaro, Anthony D'Esposito, Brandon Williams and Nick LaLota.