ARDMORE, Pa. — Just as the women’s marches and #MeToo helped define 2017, the surging numbers of female candidates have defined the midterm races now underway. Yet for all that, the November elections may not produce a similar surge in the number of women in Congress.

More than half the female candidates for House and Senate seats are challenging incumbents, who historically almost always win ; there were far more wide-open races in 1992’s so-called Year of the Woman, which doubled the number of women in Congress. A large percentage of the women now running for open seats are in districts that favor the other party. And many female candidates are clustered in the same districts, meaning many will be eliminated in this spring and summer’s primaries.

Last Tuesday’s primary elections in Ohio, West Virginia, Indiana and North Carolina help illustrate the steep path. Two women ran for Senate, both were long shots, and both lost. In House races, 27 women won — more than half. But 16 will challenge incumbents in November, 15 of them in districts firmly favoring their opponents.

Here are all the women who have filed or are expected to file to run for a House seat, according to a New York Times analysis of data from the Center for American Women and Politics at Rutgers:

If a woman wins in every district where one is running, 152 female voting members would make it to the House. That would nearly double their current share but men would still outnumber women by nearly two to one.

But many are running in districts where the opposing party is heavily favored, which would eliminate about half, leaving 171 women .

If a woman were to win in every primary in which at least one is running, 323 women would advance to the general election.

Some have already lost in primaries that have been held. 321 Democrats and 106 Republicans remain.

Each figure here represents one of the 476 women who are part of this record surge.

Six women are running in the Democratic primary this Tuesday — more than in any other congressional district in the country.

The race here in Pennsylvania’s newly drawn Fifth Congressional District, which includes South Philadelphia and the mostly affluent bedroom communities of Delaware County, shows both the energy of women in the midterms and why this election may not be a repeat of 1992.

“We are not going to see, in one cycle, an end to the underrepresentation of women in American politics that we’ve seen for 250 years,” she said. “The concern is, we need this energy and engagement to be here for the long haul. This is a marathon, not a sprint.”

“While we are encouraged by the energy and the enthusiasm and the engagement of women, I think we also at the same time have to be cognizant of the fact that many of these women, even when they win their primary, will be running very tough races in November,” said Debbie Walsh, the director of the Center for American Women and Politics at Rutgers University.

The increase in the number of female candidates tilts largely toward Democrats — at the start of this year, the number of Democratic women seeking House seats was up 146 percent from the same point in 2016; among Republicans, it was up 35 percent. And many of the women have less experience in government and politics than those who ran for Congress in the past.

Democrats in Tuesday’s House primary in Pennsylvania’s Fifth District include, from left, Rich Lazer, Lindy Li, Ashley Lunkenheimer and State Representative Margo Davidson. Michelle Gustafson for The New York Times

There are no women in Pennsylvania’s 20-member congressional delegation. And the state legislature ranks among the bottom for representation of women, hitting 19 percent this year.

“Afghanistan is 19 percent,” said Mary Gay Scanlon, one of the Democrats in the congressional race, milling between potential voters at a meet-and-greet at the home of a Democratic committeewoman on a recent Saturday morning.

But party officials worry that the six female candidates, who are largely aligned on the issues, will split the vote and hand the nomination to one of the two well-funded male candidates — one a longtime state legislator, the other a labor-backed former deputy mayor of Philadelphia.

With days to go in the race, one of the women, Molly Sheehan, said last week that the state legislator, Greg Vitali, had asked her to drop out and endorse him. Ms. Sheehan, a bioengineer at the University of Pennsylvania who has outraised Mr. Vitali and has the support of several resistance groups, argued that he would not have made a similar request of a man. (He said he had.)

Even those who dismiss the notion that women vote only for women and men for men say that with 10 candidates in the race, someone could win with a relatively small percentage of the vote. At a hard-fought Delaware County endorsement meeting recently — about 500 committee members voting in four rounds — no candidate secured the 55 percent to win.

Republicans, meanwhile, have endorsed a woman, Pearl Kim, a daughter of South Korean immigrants and a former county prosecutor and deputy state attorney general who could appeal to the well-educated women who have long been considered swing voters in the suburbs of Philadelphia.

“I honestly feel the men who stepped in are out of line,” said Rachel Amdur, the vice chairwoman of the Haverford Democratic Committee, which has stayed neutral in the race. “This is what women do, women recognize it’s not their year all the time. Men do not.”

“The drivers of the Democrats are women,” she said. “It makes me crazy that when it comes to voting, people say, ‘Oh, we’ve got to have the man.’”

Ashley Lunkenheimer, a Democratic candidate who is a former federal prosecutor and whose campaign literature prominently features her wife and three young children, agreed. “This is not us versus them,” she told the audience at the recent Saturday meet-and-greet. “But we have a moment.”

Ms. Sheehan said she was inspired to run by what she saw as the misogyny of President Trump’s campaign; she recalled sobbing next to her daughter’s crib the night he was elected. But her campaign, she said, is more about broadening economic opportunity and reducing the influence of money in politics.

“The Democratic Party wasn’t doing a good enough job fighting for working people, getting people out of poverty,” she said.

Ms. Scanlon, who served several terms as an elected school board member and leads the pro bono practice at Ballard Spahr, a large Philadelphia-based firm, led the voting in the recent endorsement contest. Speaking at the meet-and-greet, she tied women’s access to health care to women’s economic success: “At least having a woman in the room is going to raise their profile, and raise the level of the conversation.”

Ms. Kim, the sole Republican candidate, whose career has been largely spent as an advocate for victims of domestic abuse and human trafficking, said she did not hear much about gender on the trail. “Mostly, it’s people explaining to me that they’re excited to see a fresh new face,” she said.

Nationally, 422 women are still in the running for House seats, according to the Center for American Women and Politics, including some women who have not officially filed.

Of those House candidates, 55 percent are challenging incumbents, and 29 percent are running for open seats.

Female House candidates and the competitiveness of their districts RD

Candidates challenging an incumbent

Incumbents or candidates running for an open seat Solid and likely Democratic Lean Democratic Lean Republican Solid and likely Republican Toss up Solid and likely Dem. Lean Dem. Lean Rep. Solid and likely Rep. Toss up The New York Times | Note: Candidates for non-voting congressional seats are not included in this tally.

In the Senate, 49 women are running — 55 percent as challengers and 18 percent for open seats.

Women are starting from a deficit when it comes to representation in the House, because an unusually high number of incumbent women are retiring or leaving to run for other offices — 13, or a little over 15 percent of the 84 women now serving. Adding in the death of Louise Slaughter, a New York Democrat, at least 15 new female candidates will have to be elected to beat the current number of women in office; that many have not been elected since 2012.

But there has also been a similar surge in the number of men running — meaning that women still make up less than a quarter of all candidates running for the House of Representatives, up just slightly from the last election cycle.

In 1992, more than half the women who ran in primaries for Senate or House lost. Of those who won primaries, far fewer were challenging incumbents: 36 percent in the Senate and 39 percent in the House.

From left, Senators Patty Murray, Barbara Mikulski, Dianne Feinstein and Barbara Boxer, who were all elected in 1992. Charles Tasnadi/Associated Press

Another difference between 1992 and 2018 is in the kind of women who are seeking office. In 1992, more candidates had held some kind of lower office — even Patty Murray, who became an emblem of that year as the self-described “mom in tennis shoes,” had been a state legislator in Washington.

Here in Pennsylvania, Lynn Yeakel challenged Senator Arlen Specter, a Republican who had been a leader of the interrogation of Anita Hill in the hearings on the Supreme Court nomination of Clarence Thomas in late 1991, an event that drove many women as candidates, voters and donors in the midterms the next year. Ms. Yeakel had years of experience leading a group that funded charities, but no political experience, and lost by two points.

“As much as I love the story of all these new women who have emerged — and there will be some who make it — it’s a harder road,” said Ms. Walsh, of the Center for American Women and Politics. “And because they’re not as experienced, they also made choices to run in places that I think some of them, if they were seasoned political women, would say, ‘That’s not an opportunity for me.’”

Some of the best chances for gains may be among Republicans. The most promising candidate coming out of Tuesday’s primaries was Carol Miller, running for an open House seat in West Virginia that leans Republican. In the Senate, several of the incumbent women are Democrats in tossup races; but if Republicans can hold the seat being vacated by Senator Bob Corker of Tennessee, Marsha Blackburn, now a House member, would occupy it.

“As the primaries evolved, the chances of electing a significant number of women have become more difficult to see,” said David Landau, the chairman of the Delaware County Democrats.

Those who warn about a wave of women’s losses in November say they do so to temper expectations, not to discourage women from seeking office.