It was a moment that almost went undocumented, but photojournalist Melina Mara took the wrong door out of the Capitol and captured an image that would be one of the most emblematic of the story she hoped to tell: the rise of women in the U.S. Senate.

The photo shows a woman leading a young girl by the hand toward a wall of dark-suited men. That woman was Sen. Kay Bailey Hutchison, R-Texas, bringing her daughter to a 9/11 commemoration ceremony where her fellow senators were lined up on the Capitol steps.

"That image, that's kind of multilayered in the sense of the symbolism. The line of men, and the mother leading the daughter," Mara said. "It doesn't matter what the mother is, whether it's a politician. It's a mother leading the daughter, and just doing it and saying, 'We're going through the wall.' "

The photo of Hutchison and her daughter is one of 38 in "Changing the Face of Power: Women in the U.S. Senate," an exhibit that will be displayed at the Maine State House today through April 8. An opening event will be held at 11 a.m. on the third-floor rotunda.

As a free-lance photographer covering the re-election campaign of U.S. Sen. Patty Murray of Washington in 1998, Mara was surprised to learn that nine women were then serving in the Senate. When Mara began her "Face of Power" project in 2001, there were 13 female senators. Now there are 14, including Olympia Snowe and Susan Collins of Maine.

Aside from an article here or there, Mara felt the mainstream press was missing the story of women's growing presence in the Senate. Some stories, like one that featured the favorite crabcake recipe of Sen. Barbara Mikulski, D-Md., or another about Sen. Maria Cantwell, D-Wa., and her mother, didn't show the real story of these women at work as lawmakers, Mara thought.

"I just knew when I was there, just knew, this was a story I had to do," Mara said. "I want to see these women doing what they do. I want to see them as lawmakers, as 24/7 lawmakers and what that entails on Capitol Hill."

The female senators were doing more than changing the look of the male-dominated institution, Mara says. They were also changing the feel of the Senate, the approach and the issues on the table, she says.

The women, Mara says, take a more bipartisan approach to lawmaking than their male counterparts, often bring a more approachable manner to the job and share a sense of camaraderie.

Mara worked on her project between 2001 and 2004, while also working on freelance assignments. About 80 percent of her time was devoted to trying to win unfettered access to her subjects. When she couldn't follow them behind official closed doors, she would wait for them to emerge or look for genuine moments in contrived events.

The 38 black and white images in the exhibit were culled from as many as 6,000 photos Mara shot. They include pictures of female senators in the corridors of power and at work behind desks or microphones, but also sharing smiles and thumbs-ups and flanked by children.

Serendipity played a particularly large role in the photo of Hutchison and her daughter. Mara shot it with a borrowed camera as Capitol police tried to hurry her away to the media area for the ceremony, which had already started. One officer was pulling Mara's arm, and another threatened to confiscate her film if she didn't get going. It was all over in about a minute, she says, but it was enough.

"Her photographs really get it," said Don E. Carleton, director of the University of Texas at Austin Center for American History, which owns the collection and is responsible for organizing the traveling exhibit. "I think it's path-breaking work because of the fact that there is a new sort of era in the Senate because of all these women. It is a different institution. I don't think the public understands that very well. I think these photos are going to change that."

Now, as a staff photographer for The Washington Post, Mara is busy covering both the men and the women around the Capitol. She doesn't think her project is really over, however.

"In my heart of hearts, I'm always watching. I'll always cover them," she said. "I'll always kind of be watching out of the corner of my eye to keep track of the story."