And her name is not Hillary Clinton.

If Clinton runs for president, New York Sen. Kirsten Gillibrand’s time won’t be in 2016. But the junior senator from New York, who holds Clinton’s former seat and is often overshadowed by the state’s better-known political figures, is quietly building a résumé that would allow her to be taken seriously should she ever decide to run for president.

As a Blue Dog Democrat from upstate New York, the former congresswoman was viewed with distrust — if not disdain — by the left when she snagged a surprise appointment to Clinton’s seat in 2009 amid fierce jockeying for the slot.

( Also on POLITICO: How well do you know Kirsten Gillibrand?)

Since then, the 46-year-old Dartmouth-educated attorney has demonstrated impressive political chops. She has managed not only to ease liberals’ misgivings about her but also to win their enthusiastic support — all while maintaining her moderate cred and doing the kind of behind-the-scenes political scut work that could enable an eventual national bid.

“I find her to be very impressive,” said the champion of the left circa 2004, Howard Dean. “She often underwhelms people at first sight, [but] when you look under the hood, you find a first-class political mind and someone who has a great deal of skill.”

After skating to a full term in November, Gillibrand told President Barack Obama he would be wise to foster closer ties to the Senate’s 20 female members; he heeded that advice by having them over for dinner at the White House on Tuesday night. She recently hosted a fundraiser for Elizabeth Colbert Busch, the underdog-turned-favorite in a special House election in South Carolina against Republican Mark Sanford next month.

( Also on POLITICO: 2016: Who’s next?)

Gillibrand’s standout move in the 2012 election cycle was through one of her PACs, the female candidate-centric Off the Sidelines, which helps galvanize support and fundraising for women candidates.

It’s a form of grass-roots list-building that would benefit a potential Democratic presidential candidate. The PAC serves some of the same purposes as more-established groups, like EMILY’s List, which promote and endorse women candidates.

“We love Kirsten Gillibrand,” EMILY’s List President Stephanie Schriock said, adding that Gillibrand’s PAC has augmented her group’s own efforts.

Schriock added that she believes the PAC is motivated primarily by Gillibrand’s desire to help women get elected, not her own political future. It raised $1 million for women last cycle, primarily online, Gillibrand’s aides say, with the biggest share going to Missouri Sen. Claire McCaskill.

Of course, Gillibrand, who declined to be interviewed and whose aides are careful to publicly tamp down speculation about national ambitions, has some obstacles standing in the way of a national run. She has the misfortune of being boxed in not just by Clinton, who is seen as something of a foregone conclusion as the 2016 front-runner, but by New York Gov. Andrew Cuomo, with whom Gillibrand once worked when he was secretary of the Department of Housing and Urban Development. She is relatively unknown nationally.

And if Clinton runs in 2016, Gillibrand’s next chance at running wouldn’t be for another eight years — a lifetime in politics, even for a younger senator.

Remove those issues, and she would be seen as a first-tier presidential candidate by most metrics — especially at a time when both parties are eager to find strong female prospects for the White House.

In an interview ABC News’ Diane Sawyer did with the 20 women senators sworn into office earlier this year, the news anchor asked if there was a future president sitting among them. Hawaii’s Mazie Hirono, seated next to Gillibrand, draped an arm around her New York colleague with a smile.

Other names are mentioned more frequently — newly minted Sen. Elizabeth Warren of Massachusetts has become the wished-for female alternative to Clinton in some quarters — but Gillibrand is clearly in the conversation. Her campaign to overturn the military’s “don’t ask, don’t tell” policy, launched shortly after she joined the Senate, made Gillibrand a hero of the gay rights community and established her as a young Democrat on the rise.

Barely more than four years ago, as a relatively new congresswoman from upstate New York, Gillibrand was tapped by then-Gov. David Paterson to replace Clinton. Gillibrand was elected to a rural House district in 2006, a Democratic wave year, claiming the seat that had been held by four-term Republican Rep. John Sweeney. She was reelected in 2008.

Gillibrand is “a tenacious fighter, as demonstrated by her work to pass [the repeal of] ‘don’t ask, don’t tell,’” said Center for American Progress president Neera Tanden, a former Clinton adviser who hopes the former first lady will run in 2016.

“Her leadership was critically important there, and I think she’s planning on engaging even more on women’s issues,” she said of Gillibrand. “She’s smart and aggressive.”

“Aggressive” has often been used pejoratively by Gillibrand’s colleagues to describe her ambition. During her first congressional term, some House colleagues compared her to Tracy Flick, the grating, driven-to-succeed high school student played by Reese Witherspoon in the 1999 film “Election.”

Gillibrand’s interest in electing women, however expedient it might be politically, is rooted in her background — her grandmother, Dorothea Noonan, was a major figure in Democratic politics in Albany, often cited as the power behind the male throne of Mayor Erastus Corning, with whom she had a close relationship.

Gillibrand later worked as a corporate lawyer and at HUD when Cuomo was the Clinton-appointed secretary .

For the Senate appointment, the jockeying between Gillibrand and supporters of Caroline Kennedy for the slot was intense, and several sources at the time said the Clintons preferred Gillibrand — Kennedy endorsed Obama in the 2008 election.

The state’s liberal base was against her, but she made a full pivot on a series of issues in time to prevent a primary challenge from the left, starting by seizing on the repeal of “don’t ask, don’t tell.” She spent years working on it, pushing unsuccessfully for a cloture vote in 2009 but sticking with the issue.

Supporting gay marriage was her earliest position shift to the left — she eventually followed on other issues, such as gun control. Gillibrand once had a high National Rifle Association rating and talked about having guns under her bed but has since worked on gun control measures. Still, she has remained center-left on certain issues, including maintaining a good relationship with her state’s business community.

“If Hillary doesn’t run, I think there’s going to be a legitimate woman candidate, and it’s likely to be Kirsten Gillibrand,” Dean said. She has “changed her positions,” he said, but “she doesn’t do it in a way that seems to alienate her base.”

Gillibrand’s embrace of overturning “don’t ask, don’t tell” and women’s rights appeal to a huge swath of the Democratic primary electorate — a boon should she eventually wage a national bid. Though she has never played on the national stage, she enjoys the fundraising base of New York — and her list-building activities have only helped.

“I myself don’t believe she’s positioning herself for anything because she knows that there are two prominent New Yorkers ahead of her — first, Hillary Clinton and then Andrew Cuomo,” said Richard Socarides, a gay activist who worked in the Clinton White House.

“But there is no question that she has been a star, especially on issues like gay rights, where she has really played an extremely important leadership role, but also behind the scenes and on women’s rights, guns, fairness in the military and the economy overall,” he said.

“It may look like she’s positioning herself, because she is a natural leader, and when she is passionate about an issue, I think her inclination is to make a lot of noise and try to find a solution,” Socarides added. “She’s rather fearless. She’s not risk-averse, like most people in politics.”