WASHINGTON — Medicare for All. A federal jobs guarantee. The “Green New Deal.” No Super PAC money. No mass deportations.

And, of course, a candidate who can beat President Trump — right?

After a 2018 midterm election that energized the left, perhaps the most consequential political question facing the Democratic Party is whether liberals will insist on imposing policy litmus tests on 2020 presidential hopefuls, or whether voters will rally behind the candidate most capable of defeating the president even if that Democrat is imperfect on some issues.

These dual priorities — and which one is emphasized more in the coming primary races — will help determine how the party approaches 2020. Will candidates sprint to the left on issues and risk hurting themselves with intraparty policy fights and in the general election? Or will they keep the focus squarely on Mr. Trump and possibly disappoint liberals by not being bolder on policy?

The two paths may help determine the electoral fortunes of potential left-wing candidates like Senator Bernie Sanders and more moderate ones like former Vice President Joseph R. Biden Jr., as well as Democrats like Senator Kamala Harris and Beto O’Rourke who have a history of appealing to both liberals and moderates and drawing ire from some leftists for not being aggressive enough on policy.