Greg Sargent WaPo column:

In a recent interview, President Trump repeatedly refused to say whether he will accept the outcome of the voting this fall, while claiming vote-by-mail will “rig the election.” So it’s easy to imagine various nightmares: Trump might declare himself winner while many mail ballots remain uncounted, or refuse to concede if mail ballots tip the outcome against him, claiming a stolen election.

A coalition of progressive and liberal groups is now gearing up for the possibility of scenarios just like those.

The coalition — which is called “Protect the Results” — now includes two dozen groups. Among them: Stand Up America, Indivisible, Communication Workers of America, Citizens for Responsibility and Ethics in Washington, Community Change Action, MoveOn, and Republicans for the Rule of Law.

Their plan: To begin building a grassroots network now that can be mobilized if any such nightmare scenario does materialize, to immediately put a big show of force into the streets to push back….

If the race comes down to one or two states — say, Wisconsin and Arizona are up in the air, or Florida is very close — and Trump retains an incredibly narrow lead on election day with large numbers of mail ballots still uncounted, Trump could declare victory.

If so, a lot depends on what elected Republicans say and do. With the base pressuring them to side with Trump in crowning himself the winner, a mass mobilization against this might make it harder.

“The extent to which it’s clear that the public is not going to accept attempts to manipulate election outcomes is going to weigh on leaders across the board,” Hasen told me. “Public protest is an important part of preserving democracy when elected leaders are breaking norms.”

A second scenario involves the media. As a group of elections experts recently pointed out, a tremendous amount is riding on whether the media adequately communicates it to the public if very large amounts of mail ballots remain uncounted on election night.