The move is one of several changes the campaign recently has made in key early states.
The former vice president and the Vermont senator clashed in separate appearances before Philadelphia AFL-CIO members, repeating their debate disagreement.
Dozens of events are planned as presidential hopefuls race toward a Sept. 30 fundraising deadline.
An uncomfortable topic that has lingered just below the surface of the primary for months erupted into clear view before millions of Americans on national television.
Under the plan, expected to be released in the next month, the federal government would pay off past-due medical bills; no funding source has yet been identified.
Like other candidates for the Democratic nomination, the independent from Vermont has sought backing from organized labor, which largely has declined to offer formal endorsements at this point.
Is that really what voters want?
The candidates must walk a tightrope, posing with the butter cow while talking gun control and Trump.
Democrats were once afraid to alienate firearms owners. Now they are pushing sweeping policies — and framing them in highly personal terms.
Ellison (D-Minn.) denied allegations that he abused a woman with whom he had a romantic relationship.