Experts predict little drama between the two Democratic progressives, but they could come under fire from the other candidates.
DETROIT — Few things illustrate the fundamental shift of the Democratic Party as much as the debate stage lineup Tuesday night. Senators Elizabeth Warren and Bernie Sanders splitting center stage — and the sweeping progressive agendas they've popularized now literally at the center of the party's ideological struggle.
Though Sanders and Warren are both jockeying for top spots in recent polls — sometimes at the expense of the other — advisers inside and close to both campaigns have little, if any, expectation for drama between the two progressives. But flare-ups could ignite against them and the ideas they espouse.
"I do expect some fireworks," Adam Green, whose Progressive Change Campaign Committee has backed Warren, told NBC News, "but not between them."
He predicts instead that "Warren and Sanders will be a one-two punch...mutually reinforcing each other's call for a bold, progressive, transformational presidency."
Advisers and strategists see the potential for the first night of the debate to turn into a referendum on Warren and Sander's agenda on issues, like universal childcare and "Medicare for All," policies others on the stage, like former Rep. John Delaney and former Colorado Gov. John Hickenlooper, have railed against as "socialism."
"There are other candidates on that stage, and also the next night, who believe in a middle ground approach, so I think like you're going to have Elizabeth Warren and Bernie Sanders end up agreeing on a lot of fundamental policy issues," Sanders' campaign manager Faiz Shakir told NBC News.
For Sanders, it's less about the progressive base he's competing with Warren for and more about drawing a contrast against someone not on Tuesday night's debate stage — former Vice President Joe Biden.
Sanders will not be able to have the on-stage confrontation with Biden that his top advisers prepared him for before the first debate. However, senior advisers acknowledge a shift in strategy in the weeks since: an increased focus on "Medicare for All" on the campaign trail, leading to direct exchanges with Biden as he criticizes Sanders' signature proposal for being too disruptive.
Sanders' team wants that debate over what they call "bold and structural solutions vs. gradual incrementalism" to drive the conversation debate night, despite the absence of the former vice president.
Sanders and Warren, who are longtime policy allies and friends, have been reticent to attack each other in these early days of the primary.
That doesn't necessarily mean they're offering glowing portraits of each other, either.
Asked in a recent CNN interview what he admires most about Warren, Sanders replied that Warren is "a friend of mine and I admire the fact that we have worked together over the years on a number of issues." He added that he thinks she's "a very good senator."