Senators Cory Booker (L) and Kamala Harris listen as US Attorney General William Barr prepares to testify before the Senate Judiciary Committee on "The Justice Department's Investigation of Russian Interference with the 2016 Presidential Election" on Capitol Hill in Washington, DC, on May 1, 2019.

Few issues have divided Joe Biden and Bernie Sanders, the two top-polling 2020 Democratic presidential candidates, more than health insurance.

Sanders is pushing a "Medicare for All" bill, which would create a government-run program and end private insurance. Biden opposes eliminating the private insurance industry and would rather expand Obamacare by adding a government-run public option.

Other candidates have staked out a middle ground by calling for Medicare for All while also looking to preserve private insurance. Three candidates calling for this mixed approach also co-sponsored Sanders' bill: Sens. Cory Booker, Kamala Harris and Kirsten Gillibrand. (Sen. Elizabeth Warren also co-sponsored the bill, but she supports Sanders' desire to end private insurance.)

Other hopefuls — including former Housing and Urban Development Secretary Julian Castro, entrepreneur Andrew Yang and Rep. Tim Ryan — have said they support a Medicare for All system that preserves private insurance, but Booker, Harris and Gillibrand stand out in light of their sponsorship of Sanders' bill.

Doug Sosnik, a Democratic political strategist and former advisor to President Bill Clinton, said attempts to stake out a middle ground reflect a desire to cater to two audiences simultaneously.

Democratic primary voters are more likely to support Sanders' plan, Sosnik said, but the plan is less popular in the electorate at large. "Trump thinks that's a good issue for him to run on in the general election," Sosnik said. "He thinks he could probably use this issue as a way to reinforce his broader narrative that his opponent is a socialist."