Regardless of Chuck Schumer and Nancy Pelosi's titles—and to the comical dismay of corporate, establishment Democrats—Bernie Sanders has become the defacto leader of the Democratic Party.

Sunday in Warren, Michigan put an exclamation point on the sentence, as Sanders, alongside Schumer, brought out 8,000 people on a bitterly cold winter day to fight against Obamacare repeal.

Even the establishment media is waking up—granted a year too late.

"That's the future of the Democratic Party," Joe Scarborough, echoing Mika Brzezinski's sentiment, said on Morning Joe Monday. "He sounds just as relevant today as he did a year ago."

So, as the mainstream media opportunistically tries to Feel The Bern after ignoring Sanders when it mattered (both CNN and MSNBC recently held primetime town halls with him), you know who's become less relevant?

Senator Elizabeth Warren .

The one-time progressive rock star—who activists tried to summon to run in 2016 with hopes of bringing down Hillary Clinton—has already made moves that many inside the Beltway believe are a precursor to a run in 2020.

But, much to the shock of genius corporate journalists who continue to live in their alternate, elitist bubble and obsess over Donald Trump's tweets rather than the endless struggles of working people, the progressive movement has soured on one if its past heroes.

A majority of progressive voters and activists I spoke to during my campaign reporting were disgusted with Warren's cowardice during the Democratic Primary, where she dodged on endorsing the most progressive candidate to run since FDR.

The firebrand, anti-Wall Street Senator was wildly popular in her home-state of Massachusetts, but she decided not to endorse Sanders before the Super Tuesday primary. Sanders lost Massachusetts by less than two points, causing progressives to believe the state—and momentum—would have gone to Sanders had Warren endorsed and campaigned with him across the state.

Larger than her Massachusetts mistake, Warren's choice to passionately campaign for Clinton—the antithesis of all she proclaimed to stand against during her meteoric rise isn't a fact progressive Sanders aficionados will simply forgive and forget.

Furthermore, Warren—along with the corporate media—was inexplicably MIA during the fight against the Dakota Access Pipeline, saying nothing as thousands of unarmed, peaceful Native Americans and environmental activists were illegally arrested and shot at with tear gas, pepper spray, rubber bullets, freezing water, and grenades by de facto oil police in North Dakota.

Like her decision to conveniently endorse Clinton when Sanders was mathematically eliminated, Warren finally chose to speak out against DAPL on the same day the Army Corps of Engineers denied a crucial permit for the pipeline's completion.

This kind of calculated, Johnny-Come-Lately progressivism doesn't cut it for the millions of progressives looking to rally behind a leader as the road to 2020 narrows.

So, the time for choosing is upon Warren. She must decide: what do I truly stand for? Right now, there's a large swath of the progressive movement that's no longer sure.

She must choose between being a strong progressive who largely ignores political calculations in favor of fighting for workers and minorities, or continue serving as a one-trick pony that steals the show by yelling at bankers during congressional hearings, but isn't trusted by the movement to do much more.

Warren must decide if she is going to stand out as a progressive leader on issues that go beyond Wall Street and the rigged economy—such as ensuring clean water and safety for the people instead of unfettered profits for the oil companies.

If Warren chooses the progressive path, she'll still need to explain her dubious choices during the 2016 election and beyond.

But if Sanders decides against running in four years, Warren—in a political climate with a jarring scarcity of true progressive leaders—could have a chance to climb back up the progressive ranks and possibly serve as the movement's best chance to finally take the White House.

The clock is ticking.

Commentary by Jordan Chariton, a political reporter for The Young Turks, reporting on the presidential campaign trail. He can be seen on TYT Politics.Before TYT, Jordan was a reporter for TheWrap and TVNewser. Follow him on Twitter @JordanChariton.