Marilyn Lands, a Democrat, won a special election Tuesday for a State House seat in Alabama after campaigning on access to abortion and in vitro fertilization, underscoring the continued political potency of reproductive rights.

Ms. Lands defeated her Republican opponent, Teddy Powell, by about 25 percentage points — an extraordinary margin in a swing district where she lost by seven points in 2022. The special election was called when David Cole, the Republican who had held the seat, resigned and pleaded guilty to voter fraud.

“Today, Alabama women and families sent a clear message that will be heard in Montgomery and across the nation,” Ms. Lands, a licensed counselor, said Tuesday night. “Our legislature must repeal Alabama’s no-exceptions abortion ban, fully restore access to I.V.F. and protect the right to contraception.”

Her election, in the largely suburban House District 10 in northern Alabama, does not change the balance of power in the state; Republicans still hold supermajorities in both its House and its Senate. And the race was small, with only about 6,000 votes cast.

But the outcome and the margin add further evidence to the pile of election results over the nearly two years since the Supreme Court overturned Roe v. Wade that abortion, and, now, I.V.F., is a reliably motivating issue. Democrats are counting on abortion rights in 2024 to continue to help power wins in key states.

Alabama has banned abortion at all stages of pregnancy, with no exceptions for rape and incest. And last month, the Alabama Supreme Court ruled that frozen embryos were people with rights — upending I.V.F. care, which typically involves creating multiple embryos but implanting only one at a time, and indefinitely freezing or sometimes destroying those left over.

In response to the backlash over that ruling, the Alabama Legislature passed a law giving I.V.F. clinics criminal and civil immunity and Gov. Kay Ivey, a Republican, signed it. It did not address embryos’ legal status.

Mr. Powell, the Republican candidate, avoided talking about abortion and I.V.F. during the campaign, focusing instead on issues including education and local infrastructure. That strategy, which many national candidates have also adopted over the past two years, does not appear to have been effective.

Heather Williams, the president of the Democratic Legislative Campaign Committee, which works to elect Democrats to state legislatures, called Ms. Lands’s victory “a harbinger of things to come.”

“Republicans across the country have been put on notice that there are consequences to attacks on I.V.F.,” Ms. Williams said.

President Biden’s re-election campaign, which is planning to focus heavily on abortion as well, also highlighted the result, calling it a “major warning sign” for former President Donald J. Trump. Mr. Trump, who appointed three of the Supreme Court justices who overturned Roe, has indicated that he is likely to support a 15-week federal abortion ban.

“Voters will not stand for his attacks on reproductive health care,” Mr. Biden’s campaign manager, Julie Chavez Rodriguez, said in a statement.