Sen. Elizabeth Warren (D-Mass.) certainly is making strides to oust Sen. Bernie Sanders (I-Vt.) as the dominant figure on the most progressive wing of the party. On Monday, the Morning Consult poll shows she has ticked up two points to 18 percent while Sanders has stayed flat at 20 percent.

In addition, Working Families Party, a pro-union progressive group, which backed Sanders in 2016, endorsed Warren. Its endorsement explained, “Medicare for All. A Green New Deal. A groundbreaking wealth tax that will begin to rebalance the scales of our economy. Universal childcare. That is the Elizabeth Warren agenda, and we are proud to support it.” WFP gives a shout-out to Sanders for fighting the good fight but the message is clear: They have a better, tougher champion in Warren.

Sanders supporters responded by grousing that “national committee leaders — 56 people — held 50 percent of the voting power, with party members accounting for the other 50 percent,” as the New York Times put it. Sanders also has overhauled his New Hampshire operation.

Warren is simply a younger, brighter, cheerier candidate than Sanders with a much better campaign operation. Other than fear of a female candidate, it is hard to figure out why voters would approve the older, crankier candidate with campaign problems.

However, Warren’s ceiling may be lower than is necessary to win the nomination. The increase in Warren’s support in the Morning Consult poll has been largely driven by “four groups: the most engaged primary voters, those over the age of 65, white liberals and college-educated whites.” That would be people just like her. By vacuuming up all those voters, she may well pass Sanders (and has in some polls). However, if you assume Sanders will remain in the race with some core base of support (as he did in 2016), it’s hard to see how Warren prevails.

And that’s because former vice president Joe Biden is chugging along with 32 percent of voters and 34 percent of early primary state voters. It is easy to see why. “Among black voters, [Warren] still trails Biden by 31 points and Sanders by 11 points.” The Biden who spoke at the 16th Street Baptist Church in Birmingham, Ala., on Sunday holds the support (for now) of African American voters; the Biden in the debates doesn’t seem to register.

One silver lining for Warren: She has doubled her share of African American voters from 5 to 10 percent. Moreover, she is doggedly seeking to pursue these voters with a number of policy initiatives. That effort was recognized in her Working Families Party endorsement. (“Senator Warren has a clear vision of how race, class, and gender intersect, and her working-class background has given her deep insight into the struggles families face every day.”)

All of this comes 4½ months before the Iowa caucuses, so none of this is predictive. It does, however, point to some important questions about the shape of the race going forward:

— If Warren passes Sanders, will progressives drop him and rally to her so the left has a chance against Biden?

— If Biden does collapse, will Sen. Kamala D. Harris (D-Calif.) or another candidate be able to grab those voters and compete with Warren and/or Sanders?

— If the Democratic National Committee starts raising the bar for debates, who does that help — the single-digit candidates or one of the top-tier contenders?

— At some point (as Sen. Ted Cruz and Carly Fiorina did in 2016), do a couple of the younger candidates team up (e.g., Harris-Buttigieg, Booker-O’Rourke, Harris-Klobuchar) to make an explicit plea to the party to pass the torch?

It’s worth underscoring that the debates’ ability to significantly change the race is next to nothing. Once more we see that flashy debate performances (e.g., Beto O’Rourke) and direct attacks on Biden (Julián Castro) do nothing to change the trajectory of the race.

In every presidential election cycle, pundits and pollsters pine for a brokered convention filled with backroom deals, marathon sessions and plenty of high drama. If you had to pick a situation most likely to bring that about, it might be one in which three or four candidates cannot break away from the pack. And the greater the possibility, the less incentive any candidate with delegates has to drop out.

Could we finally get a brokered convention? Don’t rule it out.

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