Sen. Kirsten Gillibrand greets panel members from the military and the Defense Department testifying on Capitol Hill on March 13 before the subcommittee's hearing on sexual assault in the military.

Sen. Kirsten Gillibrand holds her son Henry, 4, after greeting supporters at New York State Democratic Headquarters on Nov. 6. The 2009 appointee won her first six-year term with 72 percent of the vote.

Democratic Sen. Kirsten Gillibrand of New York is introducing legislation with other lawmakers Thursday that would change how the military handles sexual assault cases. The proposal would let military prosecutors — rather than commanders — decide whether to bring serious military crimes to trial.

It's the latest high-publicity move for a senator who was virtually unknown four years ago when she was appointed to fill Hillary Clinton's senate seat. Now, she's on some lists for possible candidates for vice president — even president.

Kirsten Gillibrand has a soft voice that takes on a certain earnestness when she gets angry. Two months ago, she ripped into military officials for letting commanders decide which sexual assaults to bring to trial.

"If the convening authority is the only decision-maker of whether a case goes to trial or proceeds and the only decision-maker about whether to overturn a case, well, then all that training and all those excellent lawyers and prosecutors you have don't ... make a difference," Gillibrand sputtered during a committee hearing on sexual assault in the military in March.

Senate Majority Leader Harry Reid once called her the "hottest member" of the U.S. Senate. But friends say the woman has scary grit — precisely the kind of person who can go head-to-head with the military about how it's handling sexual assault.

Just ask former Rep. Jane Harman of California, who watched a very pregnant Gillibrand work through a committee session while enduring 12 hours of pre-labor pains. Gillibrand was in the House then.

"As self-appointed mama-in-chief, I said, 'Kirsten, go to the hospital.' 'Oh no,' she said, 'I'm fine, this is my second child, I'll be fine,' " Harman recalls.

Only hours later did Gillibrand finally leave the Capitol, and she ended up giving birth to her second son in the middle of the night.

When former Gov. David Paterson of New York first announced in 2009 that he was appointing someone from upstate farm country to take Clinton's Senate seat, there was a collective "What?" from a lot of New Yorkers. Gillibrand didn't have the star power of Clinton or of Caroline Kennedy, who was briefly interested in the job. But Gillibrand says she just kept her nose down and worked as hard as she could to prove her detractors wrong.

"I'm very ambitious. I'm very aggressive. But I do it in a really nice way," Gillibrand says with a laugh. "But you need that passion if you're going to get anything done. If you're not willing to fight for someone or fight for an issue, it's not going to happen."

She has a high tolerance for pain to get things done. Gillibrand spent about a decade and a half at two corporate law firms in New York City, putting in grueling hours. In college, she studied Mandarin — a language that takes hours upon hours of rote memorization to learn. Her squash coach at Dartmouth, Aggie Kurtz, noted that Gillibrand started out freshman year totally new to the game, but practiced hard and competed intensely to become undefeated her senior year.

Rep. Steny Hoyer of Maryland, the second highest ranking Democrat in the House, was one of the people who had made a personal call to Gov. Paterson to push for Gillibrand to get the Senate job. Hoyer says he was impressed with the way she worked a crowd, how easily she could relate to people.

"I think she also is very disciplined and focused and understands politics," Hoyer says. "She understands, for instance, who she represented in the House. She understands who she represents in the Senate."

When she moved to the Senate, for example, she quickly revised her position on guns. She had high ratings from the NRA when she represented her rural House district but became a vocal supporter of gun control as a senator.

What supporters like Hoyer see as just good politics, her critics see as lack of conviction. But Gillibrand says if you look at her legislative priorities, you can see a common thread — women and families. She'll be introducing legislation for better paid family leave, equal pay for equal work and affordable day care.

"Sometimes people say, 'Well, why do you just focus on women's issues?' Well, why do you focus on issues that pertain to 52 percent of the population? It's pretty important. And women are such the untapped potential in this economy," says Gillibrand.

Gillibrand raised more than $1 million during the last election cycle for 15 other female candidates. It's one reason why political action committees like EMILY's List love her. President Stephanie Schriock says Gillibrand is an adept fundraiser because she's intensely persistent.

"She works very, very hard," says Schriock, "and I think part of the reason she works so hard is she's got to get a lot done so she can get home at night and see her kids."

Gillibrand essentially operates as a single mom during the work week because her husband's job keeps him in New York City during the weekdays. Friends marvel at her multitasking skills — she manages to get home early nearly every night to cook her two sons dinner, get them bathed, read them books and put them to bed.

But is this woman the stuff presidential candidates are made of?

Hank Sheinkopf, a longtime Democratic strategist, says those presidential whispers are way premature: "The problem here in New York is that if you said to someone 'Who's the U.S. senator?' they would say 'Chuck Schumer.' Is she captivating? She's smart. Is she overwhelming? No. Is it a nice dream? Yeah. But could anything happen? Sure."

Last fall, Gillibrand won her first full Senate term with 72 percent of the vote. That's better than Sen. Schumer has ever done.

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