The key issue: Who can defeat Trump?

The famous Yogi Berra had it right. “The future,” observed Berra, “ain’t what it used to be.” Which is why the past is an imperfect predictor of what’s in store, especially when it comes to politics.

Even so, those of us old enough to remember the exultation on the Democratic left that propelled liberal Democratic Sen. George McGovern to the 1972 Democratic presidential nomination — and his ensuing electoral annihilation by incumbent President Richard Nixon — may be forgiven for regarding the specter of Sen. Bernie Sanders as this year’s Democratic nominee as deja vu all over again.

There is one dominant issue for Democratic primary voters prepared to think clearly and willing to do so. It isn’t how in an ideal world we best and most quickly expand affordable health care, or make education accessible to the unrich, or roll back income inequality. None of that will happen in the foreseeable future if Donald Trump is re-elected. If the candidate who makes progressives most excited ends up as the Democratic nominee, what we are actually looking at is a likely second Trump inaugural, and four more years of the most dangerous, most damaging president in history. To the extent that Trump is not already able to operate with impunity, he will be able to do so, with a Senate under Mitch McConnell’s lock and key, the House quite possibly under GOP control and the federal courts owned by Trump’s judicial appointees for a generation.

The only issue that truly matters is: Who is the Democratic candidate likeliest to save America from this entirely plausible scenario?

The rapture of college kids at McGovern rallies in 1972 didn’t translate into support across the country. Richard Nixon won re-election by the largest margin of any president in American history: Fewer than 40% of Americans voted for McGovern, who lost every state except for Massachusetts. The country was saddled with a crook, but only for another 19 months, and it was a crook who in retrospect looks like George Washington compared to Trump. Democrats voting on Tuesday ought to beware of the Bernie Bros. The stakes couldn’t be higher.