With two election cycles after the decision in Dobbs v. Jackson Women’s Health Organization under our belts, it cannot be denied: Abortion rights are the dominant issue in American politics. And when supporters of abortion rights — a clear majority of Americans — see a connection between their votes and protecting what was once guaranteed by Roe v. Wade, they are more likely to vote.

With a second Trump term possibly hanging in the balance in next November’s election, these are lessons Democrats must seize.

Abortion rights won big on Tuesday night. In Ohio, a constitutional amendment enshrining protections for abortion rights was on the ballot, and in Virginia, control of both chambers of the state legislature was considered a tossup, and both parties made abortion rights the central issue of their campaigns. The pro-abortion-rights measure in Ohio passed by a wide margin. In Virginia, the Republican governor, Glenn Youngkin, made his proposal for a ban on abortions after 15 weeks of pregnancy the central argument for electing Republicans in the state legislature. Republicans failed to win back control in the Senate and lost their narrow majority in the House of Delegates as turnout surged to historically high levels in key swing districts.

Before this week’s elections, most of the attention of the political class and the public was focused on national polls showing Donald Trump holding a lead over President Biden in the 2024 presidential contest. But it is now clearer than ever that the backlash against the Dobbs decision — and voters’ general distaste for strictly limiting abortion access — could play a crucial role in winning Mr. Biden a second term. Certainly, there will be many other major issues at play in this election, including war and voters’ perceptions of the economy. But abortion could plausibly be the deciding factor next November.

Mr. Trump’s narrow lead in recent polls is largely due to Mr. Biden’s underperforming with younger voters and voters of color relative to his support levels in 2020. While there is evidence that these polls overstate the risk to the president’s coalition, perhaps more important, these voters have proved over the course of the past year that they are highly mobilized by abortion rights and will provide strong support to candidates who share their position on the issue. By analyzing the individual-level turnout data from post-Dobbs elections, we know that women and younger voters are most likely to be inspired to vote when they see an opportunity to defend abortion rights and that this coalition is broad and diverse, including a large segment of voters of color.

To date, the post-Dobbs political battles have been fought almost exclusively at the state level. Republicans in Congress, with control of the House of Representatives, have shown little appetite for passing a federal ban, saying the issue is best left to the states to decide. The implausible path for such legislation through a Democratic majority in the Senate, not to mention a certain veto from Mr. Biden, has spared the Republican majority in the House from any substantial pressure to advance such legislation. That said, in the immediate aftermath of seeing his state overwhelmingly support abortion rights this week, the Republican senator J.D. Vance of Ohio is urging a national Republican position on abortion in the form of a 15-week ban.

The base of the Republican Party clearly expects its candidates to prioritize abortion bans. To ignore these calls is to risk a demoralized base on Election Day next year, making the path to victory that much narrower for a party that has won the national popular vote for the presidency only once in the past 35 years. Yet at the same time, the 2022 and 2023 elections have proved that standing firm in support of abortion bans energizes progressive voters and swings independents toward Democratic candidates. Given that Mr. Trump faces the challenge of expanding his coalition beyond that of his 2020 shortfall, such a development could doom his hopes of returning to the White House.

Mr. Biden and his team have no doubt grasped this dynamic and will presumably force Mr. Trump to pick one of the two daunting paths before him. Before the Virginia elections, national Republicans clearly hoped that Mr. Youngkin had found the consensus choice, with what they emphasized as limits on abortion, not bans. These hopes were dashed in polling places across Virginia on Tuesday, something that surely did not go unnoticed in the White House.

Abortion rights have had the biggest impact on elections over the past year and a half where voters believe abortion rights to be threatened and when they plausibly see their votes as a means to protect or reinstate abortion rights, it is good news for Democrats and for expanding or protecting abortion access. States with abortion on the ballot in the form of ballot measures have seen the biggest effect, but similar effects have been felt in states like Pennsylvania, Nevada and Arizona, where the issue was at the forefront of campaign messaging.

While Republicans find themselves boxed into a corner on the issue of abortion, in many ways Mr. Biden is the ideal messenger to connect the dots for moderates on this issue. His personal journey on abortion rights has been well documented and mirrors that of many Americans. This year Mr. Biden said: “I’m a practicing Catholic. I’m not big on abortion. But guess what? Roe v. Wade got it right.” Polling shows a sizable portion of moderates and even conservatives more or less agree with him: They may not consider themselves activists on the issue of abortion rights, but at the same time, they are deeply uncomfortable with the Dobbs decision and how it stripped so many Americans of individual freedoms.

This presents both a challenge and an opportunity for Mr. Biden in 2024: Republicans are on the defensive when it comes to abortion rights, and are losing ground every day. Mr. Trump, in calling bans on abortion after about six weeks of pregnancy “a terrible thing and a terrible mistake,” has shown he is aware of the liability the issue represents for his presidential campaign. Yet he is left without a solution that will mollify his supporters while not alienating moderates or mobilizing progressives.

Democrats exceeded expectations and precedent in key races in 2022 and 2023 by putting abortion rights and Republican extremism front and center. In 2024 all voters must understand that their votes will decide the future of abortion rights, everywhere.