They still wear suffragist-white outfits and cheer on the prospect of “Madam President.”

But eight years after Hillary Clinton became the first woman to lead a major party’s presidential ticket, Democrats are sending American women a more sober and urgent message even as they try to elect another barrier-breaking candidate.

Republican policies, they argue, have had disastrous and once-unthinkable consequences for the health and autonomy of women and their families since the overturning of Roe v. Wade. A second term for former President Donald J. Trump, they warn, would be even more dangerous.

“Simply put,” Vice President Kamala Harris said this week from the stage of her party’s convention, “they are out of their minds.”

From the women who described harrowing pregnancies and their difficulties receiving medical care to Ms. Harris’s finale on Thursday night, the tone and emphasis were a radical departure from the optimistic feminism and chants of “I’m with her” that dominated Mrs. Clinton’s 2016 campaign.

“This is a time where the rights of women are fundamentally under attack as it relates to abortion, I.V.F., when and how to have a family,” said Senator Laphonza Butler, Democrat of California and a close Harris ally. “It’s not about minimizing the importance of race or gender. It is about appreciating that in this moment in the history of our country, this election is bigger than anybody’s race or gender.”