The senator who most consistently has opposed President Donald Trump’s appointees is not a famous liberal firebrand such as Bernie Sanders (I-Vt.), Elizabeth Warren (D-Mass.), Al Franken (D-Minn.), or Chuck Schumer (D-N.Y.).

Instead, it is New York’s junior Democratic senator, Kirsten Gillibrand, who took office in 2009 with a reputation as a moderate after two years in the House of Representatives. With the confirmation Thursday evening of Labor Secretary Alex Acosta, Gillibrand has a nearly perfect record of opposition.

“When you’re more obstructionist than Chuck Schumer, that speaks volumes.”

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She voted against Supreme Court nominee Neil Gorsuch. No surprise there; Democrats took a nearly unified stand. Her votes against other controversial nominees are no shock, either. She joined all of her colleagues in opposing Education Secretary Betsy DeVos, for instance.

Gillibrand is hardly the only Democratic senator who has tried to throw a monkey wrench into the Trump agenda. The party’s treatment of Trump’s nominees has been unprecedented.

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Even in that context, though, Gillibrand has stood out. She has opposed even nominees who have sailed through. She was among a small handful of senators who voted “no” on Elaine Chao for secretary of transportation. It is an unusual stance considering the agency is relatively low-profile, and Chao could not be a more mainstream choice. The wife of Senate Majority Leader Mitch McConnell (R-Ky.) has previous experience as a Cabinet secretary without major scandal.

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“When you’re more obstructionist than Chuck Schumer, that speaks volumes,” said Jessica Proud, a spokeswoman for the New York Republican Party.

Gillibrand was among 11 Democrats to vote against Homeland Security Secretary John Kelly and one of six to oppose Rod Rosenstein for deputy attorney general. She even opposed Defense Secretary James Mattis, the only senator to do so. She explained her “no” vote in a New York Times op-ed piece.

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“Our American democracy was built around the concept of civilian control of the military,” she wrote. “New presidents are typically allowed latitude to appoint their cabinet members. But President-elect Trump is not entitled to ignore our laws and change the fundamental government constructs that have enabled our country’s success.”

Gillibrand’s only “yes” votes have been for United Nations representative Nikki Haley and Veterans Affairs Secretary David Shulkin, who won a unanimous vote.

Gillibrand’s knee-jerk opposition to Trump’s appointees may be somewhat surprising for a politician who built a reputation as a moderate in the House after upsetting a four-term incumbent Republican in an upstate New York district that last had gone Democrat in the 1970s. But she has tacked hard to the Left since then-Gov. David Paterson tapped her in 2009 to replace Hillary Clinton in the Senate after the former first lady became secretary of state.

In the House, Gillibrand earned an “A” rating from the National Rifle Association, co-sponsoring a bill to delete gun background check information after 24 hours. She also opposed amnesty for illegal immigrants and opposed giving state driver’s licenses to illegal immigrants.

So upset were liberals about Gillibrand’s record that progressive Rep. Carolyn McCarthy (D-N.Y.) threatened a primary challenge.

In the Senate, though, Gillibrand could not shed her moderate roots quickly enough. Her NRA “A” rating quickly turned into an “F.” She co-sponsored legislation to give amnesty to illegal immigrants who came to the country as children.

Gillibrand’s record on Trump appointees has fueled speculation that she is laying the groundwork for a long-shot run for president in 2020.

“I think it’s more that she’s a tool of the Democratic Party,” Proud said. “She’s gone very Washington, for lack of a better term … You rarely even see her around New York anymore.”

James Battista, a political science professor at the University of Buffalo, wrote in an email to LifeZette that Gillibrand has moved Left.

“Certainly her behavior since Trump’s win has been noticeably different, and more clearly liberal, than it had been before,” he wrote. “She’d never been a conservative or moderate-to-conservative Democrat like, say, Joe Manchin [D-W.Va.] or Claire McCaskill [D-Mo], but she also hadn’t been thought of as a fire-breathing liberal like Warren.”

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If Gillibrand does run for president, her votes won’t hurt in the Democratic primaries — and some activists already have taken note.

“The only person who voted “no” on every Trump appointment was Senator Kirsten Gillibrand. Remember that in 2020,” tweeted Rachel Gonzalez, who was a delegate for Clinton from Missouri at the Democratic National Convention last year.

As for Trump, he has two more major appointments that require Senate confirmation votes — U.S. trade representative and chairman of the Council of Economic Advisers. If past is prologue, Gillibrand will vote “no” on them, too.