Almost every path to victory for President Biden relies on strong support from women. But his current standing among women is the weakest lead a Democrat has had since 2004, a key factor in how tight the race is.

Mr. Biden’s lead among women has slid to about eight percentage points since the 2020 election, according to an average of more than 30 polls conducted over the last six months and compiled by The New York Times. That’s down from a lead among women of about 13 percentage points four years ago.

And since the 2020 election, former President Donald J. Trump’s support among men has recovered and is back to the double-digit lead he had in 2016.

Republicans have generally held leads among men in most presidential elections going back decades. But every year that Democrats have won the presidency, they have led among women by more.

Mr. Biden’s drop in support has been particularly pronounced among Black and Hispanic women, according to a new set of polls focused on women across the country and in Arizona and Michigan from KFF, a nonprofit organization that focuses on health care research.

The surveys show that even as abortion and democracy are key issues for a small but meaningful segment of women, concerns about inflation continue to play a more central role in the race and to benefit Mr. Trump.

In states where abortion is on the ballot, however, the KFF polls offer some evidence for the Democratic theory that the issue will be a motivating factor that drives women to vote.

Mr. Biden’s support among women is still somewhat more resilient than his support among men, which has fallen further, particularly among young men and men without a college degree. And Democratic strategists insist that traditionally Democratic constituencies, including women and Black voters, will return to Mr. Biden’s side as the race goes on.

Still, Mr. Biden’s current struggles with Black and Hispanic women are especially striking. He is winning among Black women in the KFF survey by 58 percentage points, but that represents a significant drop from his 86 percentage point margin among Black women in the approach to the 2020 election, according to an average of New York Times/Siena College polls from that election. Mr. Biden’s lead with Hispanic women has also shrunk substantially, to about 12 points. The survey found Mr. Biden’s lead among women overall to be four points.

“Once the campaign kicks into high gear, abortion will rally the women,” said Celinda Lake, a Democratic pollster who has been studying women’s voting behavior for decades. “And as much as Trump wants to right-size himself, he can’t stop himself from bragging about how he overturned Roe v. Wade.”

In states like Arizona, where abortion is restricted and may be on the ballot in the fall, Democratic women were more motivated to vote than in states where abortion access was not at risk, the KFF surveys found. Among Republican women, there was no difference in motivation.

In Michigan, which voted to affirm abortion rights in 2022, Mr. Biden is performing slightly worse among women compared with Arizona, noted Ashley Kirzinger, the associate director for polling at KFF.

“It’s not just that Biden is more popular in Arizona — he’s not,” Ms. Kirzinger said. “Michigan women are no longer worried about abortion access, and Biden does worse in that scenario.”

Abortion-focused voters tend to be younger and whiter than women overall, the KFF polls found. They approve of how Mr. Biden is handling abortion and would like to see him re-elected.

But the much larger group of women who say inflation is essential to their vote might decide this election.

“Women are not single-issue thinkers,” said Kellyanne Conway, a Republican pollster, Mr. Trump’s former campaign manager and a co-author, with Ms. Lake, of a book detailing the political desires of women. “Therefore, they are not single-issue voters.”

“Joe Biden and the Democrats seem to only talk to women from the waist down, since abortion is the only issue Joe Biden has an edge on in the polls,” Ms. Conway added.

Inflation voters are more likely to be Black or Hispanic than women overall. They are more likely to be middle-aged. In Michigan, nearly 60 percent of Black women say inflation is the most important issue to their vote. A similar share of Hispanic women in Arizona say the same. For these women, inflation blows all other issues out of the water.

Overall, twice as many women say they were better off financially under Mr. Trump, the KFF surveys found. Young women, a key constituency that Democrats are hoping to retain this cycle, were nearly three times as likely to say things were better for them financially under Mr. Trump than Mr. Biden. Even so, 41 percent of young women said there was no difference between their financial situation between the two candidates. Half of Black women also said there was no difference.

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This trend of Democratic success with women is relatively modern. In the 1980s, Ronald Reagan and then George H.W. Bush won majorities of both men and women. But in the last 20 years, it has been rare for a Democrat to fall below a double-digit lead with women. The last Democrat to end a campaign with a single-digit lead among women was John Kerry in 2004.