“The politics are horrible for the Democratic Party, that’s my judgment,” said Ms. Heitkamp, who lost her seat representing North Dakota last year and is now heading up an effort to win rural voters. “We’re making the issue about our plan rather than what the president has or has not done.”
Senator Sherrod Brown of Ohio, who has said it would be a “terrible mistake” for the party nominee to support Medicare for all, is urging Democrats to embrace a more unified message against Mr. Trump. That feels unlikely in the midst of a heated primary campaign where health care has emerged as a significant difference between the candidates.
“Democrats need to start talking about the contrast with Trump on this,” said Mr. Brown, who has not endorsed a candidate in the primary race. “The conversation should not be Democrats fighting over the path to universal coverage.”
Congressional candidates are frequently asked whether they agree with the policy; candidates in all 10 of the most competitive Senate races have said they do not support it, preferring to keep their health care message focused on expanding Medicaid, protecting the Affordable Care Act and slamming repeal efforts by Republicans.
“Texans kind of don’t like to be forced into anything,” said M.J. Hegar, a Democrat running in a Senate primary in Texas. “They feel, we feel, that we are a nation and a state of freedom and choices, and that’s a big part of why the majority of Texans want a public option.”
Senator Doug Jones, an Alabama Democrat who has endorsed Mr. Biden, sought to cast himself as a check on any Democratic president who would pursue Medicare for all, a proposal that voters in his conservative state view with deep antipathy.
“If a Democrat is elected president, that Democrat is going to have to talk — not only try to reach across the aisle to Republicans to get things done — they’re going to have to also talk to Democrats like me that are more moderate,” said Mr. Jones, who is often considered the most endangered Democratic senator in the country.