President Biden's campaign is opening a field office in Hillsborough County to mobilize voters in a region where Republicans are gaining ground.

Why it matters: This is Biden's first field office in Florida and a sign that he is serious about winning the state.

Catch up quick: The campaign sees Florida as a worthy investment now that a referendum to enshrine abortion rights in the state constitution will be on November's ballot.

• Biden and other top Democrats are making appearances in Florida to blame Donald Trump for the state's six-week abortion ban.
• Vice President Kamala Harris will visit Jacksonville on May 1, when the ban takes effect.

State of play: Hillsborough is the third-largest county in the state. It's long been a swing region. But it's trending redder.

• Voters went for Biden in 2020, but Republicans swept all statewide offices and most state legislative contests during the 2022 midterms.

Meanwhile, the GOP has also been narrowing the gap in voter registrations.

• Democrats in Hillsborough only lead Republicans by 9,000 active registered voters, down from an advantage of 43,000 last year and 74,000 in 2020.

What they're saying: Matt Isbell, a Democratic elections analyst, tells Axios that Democrats must win the county in 2024 to have "any future life force" in Florida.

What to expect: The Biden campaign plans to host volunteer training sessions, canvass kickoffs and recruitment events at its field office.

• "Florida is ground zero in the fight for our rights and fundamental freedoms," says Jasmine Burney-Clark, the campaign's top staffer here, "and we're not taking anything for granted."