Bangladesh, Sept. 23 -- Former Vice President Kamala Harris's planned appearance with Michigan Democratic Senate nominee Abdul El-Sayed offers an unusual opportunity to revisit one of the most complicated policy questions in Democratic politics: how far can a candidate go in promising government-run health coverage before the details become politically difficult?

Harris and El-Sayed are scheduled to appear together in Michigan on Sept. 22 at a roundtable focused on Black maternal health. Harris endorsed El-Sayed after his Democratic primary victory, and the joint appearance is part of the party's effort to unify voters ahead of the November election.

The pairing is notable because both politicians have been associated with ambitious pr...