How Bernie Sanders and Elizabeth Warren's progressive alliance ends

Sens. Elizabeth Warren and Bernie Sanders are longtime political allies and friends, which is why they haven't yet attempted to undermine one another in the Democratic presidential primary.

But if the two 2020 frontrunners remain in the race, they'll eventually be forced to criticize each other's positions and records.

There are a few fault lines that run through the Warren-Sanders relationship, most notably concerning their positions on capitalism vs. democratic socialism.

Warren has called herself “a capitalist to my bones” and believes well-designed rules and regulations can make capitalism work for everyone. But Sanders has long described himself as a democratic socialist and believes capitalism is fundamentally unsustainable.

Fellow 2020 candidates — or voters themselves — might eventually push Sanders and Warren to debate their differing positions on our economic system.

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Sens. Elizabeth Warren and Bernie Sanders are longtime political allies and friends, which is why they haven't yet attempted to undermine one another in the Democratic presidential primary.

The two have similar positions on a range of policies and are the most progressive candidates in the 2020 race. And during July's Democratic debate, they teamed up against more moderate candidates to defend their similar visions. They'll likely attempt to do the same at Thursday's debate in Texas.

“Elizabeth and I end up agreeing on a lot of issues,” Sanders said at an April town hall.

But there are some key differences between the two that could become more exposed as the primary continues.

On healthcare, Sanders wrote the Medicare-for-all legislation that Warren co-sponsored.

But Warren was slow to fully endorse Sanders' vision on the campaign trail, sticking to talk of “universal,” rather than “single payer” care. And given the many detailed plans Warren has unveiled throughout her campaign, the fact that she doesn't have her own healthcare agenda is notable.

The two New Englanders also disagree on a few key issues related to democratic reform. While Warren would get rid of the Senate filibuster and is open to growing the size of the Supreme Court, Sanders is opposed to both.

And on a more philosophical level, Warren and Sanders also position themselves differently. Warren has called herself “a capitalist to my bones” and believes well-designed rules and regulations can make capitalism work for everyone. But Sanders has long described himself as a democratic socialist and believes capitalism is fundamentally unsustainable.

“For a number of reasons — alienation and disengagement among the electorate, and the extraordinary power of big business and finance over government — [Sanders] doesn't believe that even the cleverest, most uniformly applied regulations will solve what he views as a political and economic crisis,” Washington Post columnist Elizabeth Bruenig wrote in June.

While Sanders has long called for “a political revolution,” Warren is running on “big structural change.”

This fundamental difference will likely, at some point in this primary, come to the fore. Some Sanders' supporters, while sympathetic to Warren, believe that Sanders' vision for a grassroots revolution is key to beating Trump and changing the country's direction.

“Though Warren is an ally of many progressive causes, the best chance that we have to not just construct some better policy, but reconfigure a generation of American politics lies with Sanders running and capturing both the Democratic primary and the presidency,” Bhaskar Sunkara, editor of the far-left magazine Jacobin, wrote in The Guardian last year.

Meanwhile, many Democratic voters haven't signed on to democratic socialism and will push Warren to emphasize her faith in markets.