WASHINGTON

Senator Lisa Murkowski of Alaska, the new chairwoman of the Energy Committee, was at a reception in Hershey, Pennsylvania, last month when aides to Representative Kevin McCarthy of California, the No. 2 Republican in the House, presented her with a party favour: a black windbreaker with the words “Chairman’s Table” on the back.

There was just one problem: The windbreaker was for a man, and far too big for Murkowski. McCarthy’s aides say they simply ran out of women’s jackets in Murkowski’s size, but to her the episode reflects a new reality on Capitol Hill.

“His staff was, of course, very apologetic,” said Murkowski, who gave the windbreaker to her husband and said she took no offence. “But I did think that was somewhat telling. We are not thinking about the women.”

The November elections brought a record number of female lawmakers to Washington. With 20 in the Senate and 84 in the House, women for the first time in history hold more than 100 seats in Congress. But the Republican takeover of the Senate has also cost women powerful committee leadership posts and presented new challenges to their wielding of power.

Last year, when Democrats controlled the Senate, women led a record nine committees, including male bastions like the Appropriations Committee, which dispenses billions in federal dollars, and Intelligence, which oversees the government’s secret national security apparatus. Now there are only two female committee chairs: Murkowski and Senator Susan Collins, R-Maine.

In the House, while women hold five of the 10 elected leadership spots, only one woman — Representative Candice Miller of Michigan — leads a committee, House Administration.

The reason is largely that Congress is a culture where power is tied tightly with seniority, and committee chairmanships do not go to junior members. More than two-thirds of female lawmakers are Democrats, and Democratic women, who overall were elected earlier and in larger numbers than their Republican counterparts, have more longevity. When Democrats lost control, women lost top jobs.

“You cannot deny that women were in a more powerful position in the United States Senate when the Democrats were in control,” said Debbie Walsh, director of the Centre for American Women and Politics at Rutgers University. “It’s not to say that women can’t and won’t exert leadership, but we do know that titles matter, those formal positions of leadership matter.”

Women do of course flex their muscles regardless of rank. A revolt by Republican women recently forced House leaders to abandon a bill that would have banned abortions after 20 weeks of pregnancy. In the Senate last week, Murkowski shepherded to pass a bill to approve construction of the Keystone XL pipeline to carry petroleum from Canada to the Gulf Coast, her party’s first legislative priority in the new Congress.

“The women in the Senate — there are no pushovers here,” Murkowski said, rejecting the notion that women have lost power. “I don’t think that Barbara Mikulski” — the Maryland Democrat and former Appropriations chairwoman — “goes shrinking away because she’s not gavelling in the meeting.”

But in an institution whose core function — writing laws — rests with committees, chairmen and chairwomen wield enormous influence. They alone can call hearings, the first real step in shaping and passing legislation.

“The ranking minority member may have some wonderful ideas,” said Ross Baker, a political scientist at Rutgers University, “but unless the chair approves, it’s not going to happen.”

For Democratic women, watching the tough-talking Mikulski transition from leading the Appropriations Committee to being its ranking member has been especially difficult. Elected to the Senate in 1986, she is by far its most senior woman and has for years held bipartisan dinners for female colleagues. In 2013, after nearly three decades on the committee, she made history by becoming the first woman to run it.

“Barbara Mikulski has worked and fought and thrashed and clawed for decades to get the chairmanship of the Appropriations Committee, and to have it snatched away almost as soon as she got it, all of us feel for her,” said Senator Claire McCaskill, D-Missouri. “It’s painful for us.”

In an email message, Mikulski said she would “continue to have a voice,” adding, “While I’ve been in the minority before, I’ve never been on the sidelines.”