The news that Senate Democrats are adding Elizabeth Warren to their leadership team raises an important question about the trajectory of the party's most popular figure not named Hillary Clinton: Will she be co-opted by the establishment?

It's a query that naturally comes up every time a politician who has made their mark as an outsider joins the official hierarchy in Washington. Warren's brand relies on her popularity with liberals who believe the Democratic Party of Obama, Clinton, and another Senate leader, Charles Schumer of New York, is no less a patron of Wall Street than is the GOP. Two years after her election in Massachusetts, Warren is not nearly the nuisance to leadership that Senator Ted Cruz has been for Republicans, but she is known for speaking—and voting—her mind. Whether her appointment as a "strategic policy advisor" to the Democratic leadership changes that approach or not will be closely-watched in the coming months.

For her part, Warren betrayed no hint of hesitation in joining Reid's team. "I believe in what the Democrats are fighting for," she told reporters. "Wall Street is doing well, CEOs are bringing in millions more, and families all across this country are struggling. We have to make this government work for the American people, and that’s what we are here to fight for." In a separate email to her supporters, she said her ascension would mean "a seat at the table for all of us." Senate Majority Leader Harry Reid, who was reelected on Thursday to serve as party chief in the minority of the next session, anticipated that question as he introduced Warren to a throng of reporters in the Capitol after a soul-searching caucus meeting that lasted nearly four hours. "What do you expect her to do?" Reid asked, repeating a question he said was shouted at him earlier in the day. "I expect her to be Elizabeth Warren."