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Sen. Elizabeth Warren, hailed for years as the darling of the liberal left, lately has found herself at odds with her own party – and confounding followers with positions that have, at times, seemingly put her out of step with the base.

The Massachusetts Democrat, known for championing progressive causes like Wall Street reform and minimum wage hikes, is still refining her political brand while leaving open whether she’ll eye a 2020 run. She took heat, however, for splitting with the Obama administration and congressional Democrats this month by withdrawing support on a sweeping $6.3 billion health care bill she helped write.

The “21st Century Cures Act” passed easily in the Senate in early December and was signed by President Obama in a high-profile ceremony Tuesday. It increases funding for disease research and the opioid addiction fight, and reforms the way drugs and medical devices are reviewed and authorized by the Food and Drug Administration.

It also provides funding for the president’s Precision Medicine Initiative and Vice President Joe Biden’s “Cancer Moonshot,” as well as millions for Alzheimer’s research.

Warren-Clinton Endorsement

Warren star in the Democratic Party has lost some luster after recent missteps. (Associated Press)

Warren spoke against the bill. She argued the newest version of the nearly 900-page legislation had been overtaken by greedy pharmaceutical companies and didn’t do enough to push down drug prices.

She admonished fellow Democrats during a floor speech and told them the vote was an early test of the party’s ability to stand up to Republicans. She got more direct on Twitter, advising members of her own party: “Show some spine & fight back.”

Warren faced pressure for her position from advocates, reportedly including the Association for Behavioral Healthcare and the Massachusetts Organization for Addiction Recovery.

The bill passed 94-5. Warren opposed (though so did liberal icon Bernie Sanders).

While some of her supporters say she was too combative during the 21st Century Cures Act debate, others faulted her for not speaking up sooner on a separate controversy: the Standing Rock/Dakota Access Pipeline fight.

Since August, the Standing Rock Sioux tribe and thousands of others have been protesting the 1,200-mile, four-state pipeline built to carry oil from western North Dakota to Illinois. Those who oppose the pipeline say it will hurt the environment and is on ancient burial grounds. Energy Transfer Partners, the company behind the pipeline, says no sites have been disturbed.

Warren stayed mum for months. When she finally issued a statement several months later, shortly before the Army Corps blocked the route, she faced a burst of online trolling from the cause.

“You’re about 10 months late to the party. You’re a phony. Stop acting like you care,” one person wrote on her Facebook page.

Another chimed in, “Waiting until the last minute to say or do anything, just like you did in the primary. You’re not a leader. You’re pathetic.”

Warren indeed was hit with a similar backlash on social media after she endorsed presidential nominee Hillary Clinton over Sen. Sanders during the Democratic primaries.

When Warren tried to pivot at the time and update her Facebook page with details on her push for family leave, the section garnered more than 1,000 comments – almost all of them about her not supporting Sanders.

Jennifer Lawless, a government professor at American University, called the pushback unfair.

“When you look at the overall arc of the primary campaign, she was not a Bernie Sanders supporter who reneged her support,” Lawless told FoxNews.com. “She has never compromised any of her views leading up to the endorsement.”

Lawless also was quick to note that Sanders himself got behind Clinton. “The Democrats did it beautifully,” she said. “It didn’t necessarily work out in the end but they were unified.”

Warren’s office did not respond to requests for comment for this article.

More recently, Warren raised eyebrows for her PAC contributing $5,000 to Louisiana Democrat Foster Campbell’s Senate campaign. Campbell, who ran as a “conservative” Democrat, pitched himself as “pro-Second Amendment and pro-life” – two positions that put him at odds with Warren. In the end, Campbell lost to Republican John Kennedy.

Michael Traugott, political science professor at the University of Michigan, and Lawless described Warren’s support of Campbell as smart political strategy.

“One of the basic elements of good politics is some give and take,” Traugott said. “Under some circumstances, she is willing to wait and evaluate different dimensions.”

Lawless added, “Democrats did not win the seats [in Congress] they thought they would be able to win.” Despite policy differences, she said, Campbell would have been “one more person voting for Democratic legislation.”

Warren also committed somewhat of a gaffe in sending a message to her 2.5 million Facebook followers condemning President-elect Donald Trump for packing his economic team with Wall Street fat cats. She called out hedge fund manager Whitney Tilson, who runs Kase Capital, and said the Trump presidency would “be a bonanza for the Whitney Tilsons of the world.”

The problem is Tilson opposed Trump’s White House run. He’s also a Democrat who helped start Teach for America. And he donated to Warren’s campaign.