Away from the presidential battleground states that are claiming most of both parties’ attention, a redrawn House district in ruby-red Alabama could prove crucial to their ambitions in Washington.

Formerly a safe G.O.P. seat, the Second Congressional District is now highly competitive. For Republicans, holding it would help protect their razor-thin majority in the House. For Democrats, it offers a rare opportunity to flip a seat in the Deep South.

“Alabama is not a battleground, but this seat is,” said Representative Jasmine Crockett of Texas, a rising Democratic star who joined a panel of prominent Black women on Sunday in a church in Montgomery, Ala.

“A lot of people will try to pretend as if you don’t matter,” she told the audience. “But you do.”

The new competitiveness of the district is a direct consequence of intervention by the courts, including the U.S. Supreme Court, to recognize that Alabama had illegally diluted the power of Black voters.

And the contest there between Shomari Figures, a Democrat and former Justice Department official, and Caroleene Dobson, a real estate lawyer and Republican newcomer, will offer the first glimpse of what fair congressional representation could look like in Alabama.

For Black voters, it is a hard-earned moment of empowerment, and the result of years of litigation.

“This year, it’s different — to know that I’m part of something that’s for the history books,” said Dr. Marcus Caster, one of the Black voters who first challenged the legitimacy of the former district map. “Going to the polls on Tuesday is just going to be historic, and it’s one that holds a lot of weight and value in my heart.”

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