Sen. Kirsten Gillibrand (D-NY) Chip Somodevilla | Getty Images

Sen. Kirsten Gillibrand, D-N.Y., is mounting her 2020 presidential campaign as a liberal firebrand supporting universal health care, opposing corporate cash in politics and taking on President Donald Trump at every opportunity. A number of other Democratic presidential hopefuls are making similar plays — Sens. Kamala Harris, Elizabeth Warren and Cory Booker co-sponsored the same Medicare-for-all bill as Gillibrand, for instance. But the 52-year-old Gillibrand stands apart from her colleagues by being able to boast of having voted against the president and his interests more than any other senator, according to a FiveThirtyEight analysis. Yet Gillibrand, who has served in the Senate since 2009, also has shifted some of her positions since her days in the House, when she took more moderate and conservative positions on issues such as illegal immigration and guns. Here are the key issues she's running on as the 2020 campaign picks up steam.

Health care

As the Trump administration touts the steps it has taken to dismantle Obamacare, Democratic presidential candidates are poised to make a stronger-than-ever push for increasing government's role in the health care sector. Gillibrand, who voted to expand Americans' access to health care services in the Senate, appears to be no exception. She supported a 2009 measure to require insurers to fully cover a number of health services, and scored a win in 2015 with the passage of legislation she sponsored extending a health care program for the survivors and first responders of the 9/11 terrorist attacks. More recently, she co-sponsored Vermont independent Sen. Bernie Sanders' 2017 bill aiming to replace Obamacare by applying the over-65 government health insurance program Medicare to all Americans. Sanders himself is expected to jump into the Democratic field for 2020. A decade earlier, advocating the transformation of U.S. health care in a single-payer mold would have fallen outside the Democratic mainstream. Even in the 2018 midterm elections, Republican-allied groups attacked Democratic candidates over the "radical" health care proposal. But things are different as 2020 approaches. Gillibrand is one of four Democratic contenders to co-sponsor Sanders' Senate bill, along with Harris, Booker and Warren. "I believe that health care should be a right and not a privilege," Gillibrand said during her announcement on Colbert's talk show.

#MeToo

Gillibrand's early willingness to condemn allegations of sexual misconduct — even against her political allies — won her the nickname "the #MeToo senator." In late 2017, she became the first Senate Democrat to call on her colleague, Sen. Al Franken, D-Minn., to resign after he was accused of attempting to grope or forcibly kiss multiple women. Franken voluntarily left the Senate at the beginning of 2018 as the pressure mounted from dozens of his Democratic colleagues, although he denied the allegations against him. Near the height of the #MeToo movement's influence on Capitol Hill, Gillibrand again broke ranks with her party when she said that former President Bill Clinton should have resigned over his in-office affair with White House intern Monica Lewinsky. Those actions have prompted a mix of praise and scorn from Democrats — which reportedly include some Democratic donors — but have also immunized her from accusations of partisanship when calling on Trump himself to resign over allegations of sexual assault. "Those are very credible allegations of misconduct and criminal activity, and he should be fully investigated and he should resign," she said of the president in a late 2017 interview on CNN. More than a dozen women have publicly accused Trump of inappropriate behavior including sexual misconduct; Trump has denied the allegations.

Political shift

Gillibrand hasn't always sold herself as a liberal crusader. During her short tenure in the House of Representatives, Gillibrand represented an upstate New York district and was known as a member of the more conservative "Blue Dog" coalition of Democrats. She held an "A" grade from the National Rifle Association, and once told reporters that she slept with guns under her bed. On immigration, Gillibrand opposed amnesty for illegal immigrants and supported legislation to make English the "official language" of the U.S. Once she was appointed to Clinton's Senate seat, however, Gillibrand took an about-face on both issues. The NRA quickly revised Gillibrand's perfect score to an "F" after she began consistently voting against the powerful gun lobby's interests. And where she once took a more hawkish immigration stance, Gillibrand in June espoused the controversial view that Immigration and Customs Enforcement, or ICE, should be abolished. Gillibrand has explained that her swing toward her party's left flank came from exposure to ideas and communities outside of her House district. "After I got appointed [to the Senate], I went down to Brooklyn to meet with families who had suffered from gun violence in their communities," she said of her flip on gun policy during an interview on CBS' "60 Minutes." On her new immigration stance, Gillibrand said "I came from a district that was 98 percent white ... I just didn't take the time to understand why these issues mattered because it wasn't right in front of me. And that was my fault. It was something that I'm embarrassed about and I'm ashamed of."

Economic populism