Democrats are optimistic about their prospects for this November's congressional midterm elections. But, as I argued in The Wall Street Journal last week, the party's growing (and increasingly powerful) progressive base may well decide to sit on their hands, staying home on Election Day — just as a determinative number of Bernie Sanders' supporters did in 2016.

Don't be mad at them. Would you vote for a party that promised you nothing whatsoever?

To avoid again snatching defeat from the jaws of victory, Democratic leaders must energize their long-neglected base. They should take their cue from Newt Gingrich in 1994 by nationalizing the election with an unapologetically left-leaning platform promising substantial change if they take back the House and/or Senate. Item one seems obvious: they should promise to impeach President Donald Trump.