Less than two months out from the Iowa caucus, the Democratic primary has become a four-way race featuring Joe Biden, Bernie Sanders, Elizabeth Warren and Pete Buttigieg. But while a recent war of words between Warren and Buttigieg has done little to bolster the prospects of either, it has served to underscore what makes Sanders such a unique candidate—more specifically, his remarkable consistency.

In case you missed it, Warren said this about Buttigieg last Thursday: “The mayor should be releasing who’s on his finance committee, who are the bundlers who are raising big money for him,” adding that Buttigieg should “open up the doors so that the press can follow the promises he’s making in these big-dollar fundraisers.” Earlier, Warren had complained that Buttigieg had “not released the names” of his corporate clients when he worked for three years at the controversial McKinsey & Co. consulting firm.

Warren was completely correct here. In the face of demands for transparency, Buttigieg had declined to name his corporate clients, claiming he was bound by a non-disclosure agreement. On Monday, amid sustained public pressure, Buttigieg released a full list, including Blue Cross Blue Shield Michigan, Best Buy and the Canadian supermarket chain Loblaws, among others.

Meanwhile, big money continues to flood into the South Bend, Indiana, mayor’s campaign from corporate executives, lobbyists and billionaires. While Warren and Sanders don’t hold events for wealthy donors, Buttigieg and Biden do. But unlike Biden, Buttigieg had denied the press access to those events. On Monday afternoon, the Buttigieg camp gave into Warren, announcing it would name its bundlers and allow reporters into his numerous high-dollar fundraisers.

Returning fire at Warren last week, the Buttigieg campaign labeled the Massachusetts senator a “corporate lawyer” and demanded that she release her tax returns prior to 2008—years in which she earned outside income representing corporations as a law professor.

Warren did work for some big corporations while also representing consumer interests, and on Sunday, she provided the details of her legal work, compensation included. Warren, it should be said, has been far more transparent than Buttigieg. Still, it probably wouldn’t hurt for her to further discuss her legal career, particularly when she was a registered Republican.

While I’m impressed by Warren’s campaign and supportive of her far-reaching proposals to tax the wealthy to fund programs benefiting poor, working-class and middle-class people, Buttigieg highlighted—albeit in a hypocritical and overheated fashion—the main concern I have about her: Her past career as a legal scholar who supported the “Law and Economics” movement that preached a corporate-friendly, free-market ideology.

Both Biden and Sanders have longer and more consistent histories than either Warren or Buttigieg. But while the former has spent his career defending corporate interests, the latter’s history is unabashedly progressive. Biden was among the minority of Democrats in Congress who supported the devastating NAFTA trade pact; Sanders led its opposition. The then-senator of Delaware also voted for media conglomeration via the Telecommunications Act of 1996 and supported Wall Street deregulation that led to the Great Recession. Biden has long served the interests of banks and credit card companies and was instrumental in the passage of a 2005 bankruptcy bill that continues to harm those with student debt. Warren, for her part, vigorously opposed the legislation.

Biden’s civil rights record is spotty at best. He has proudly championed the notorious 1994 crime bill as the “Biden Crime Bill,” diverging sharply from Sanders at the time. In 2002, Biden was the most prominent Senate Democrat to push for George W. Bush’s disastrous invasion of Iraq, while the Vermont senator helped lead the anti-war opposition in Congress.

Sanders’ history, by contrast, is beyond reproach. He’s been a fighter for the most vulnerable Americans his entire life in public office, not to mention a champion of civil rights since his college days. He has not only defended the environment and unions but resisted business-friendly trade deals that undermine workers and the planet alike. His anti-imperialist bona fides speak for themselves, and as the longest-serving independent in Congress, he’s proved himself a uniquely skilled legislator willing to pull all of the levers of power at his disposal.

The Democratic establishment may bleat that he’s not even a member of the party, but it is his independence that attracts the young and the disaffected. If defeating Donald Trump is their first priority, Warren and Buttigieg supporters would be wise to take note.