Over and over, Trump demonstrates why Democrats must – and should – win in 2020. And Democrats demonstrate how they can blow it, by blowing up each other over identity and ideology.

The identity question is stark: Must the nominee be female or nonwhite? Are white men – Biden, Beto, Delaney, Brown, et al – out from the start?

Notice I left out Bernie. That was deliberate. He’s not a Democrat, he was a divisive and destructive candidate last time, and nominating a socialist would be suicidal. (For this I will probably Feel the Bern online.)

Twenty, thirty or more years ago, it was a decided advantage to be a white man in the Democratic presidential race. Today it may be a disadvantage. At the very least, the playing field is level. Which it should be.

After identity comes ideology. The 2018 election results sent a surge of energy through the party’s liberals and progressives. The most compelling figure to emerge isn’t a candidate for president; she isn’t even old enough: Alexandria Ocasio-Cortez. She’s smart, tough and fearless, and she drives Republicans crazy. She can also drive Democrats crazy – for her and against her.

AOC is the force behind the Green New Deal, an audacious set of precisely the goals we need to pursue if we’re going to avoid catastrophic climate change within the next generation. It’s also precisely the kind of thing that scares the bejeesus out of more cautious Democrats, like Nancy Pelosi, who said, “The green dream, or whatever they call it, nobody knows what it is, but they’re for it, right?”

In the race now, Elizabeth Warren and Bernie are hogging the left lane. Amy Klobuchar, Kamala Harris and Beto O’Rourke have moved to the middle. John Delaney has been in the middle from the beginning. Biden presumably will be there too.

“Medicare for All” illustrates the dilemma. Progressives have made it a bumper sticker and rallying cry. Klobuchar, Delaney and Sherrod Brown have distanced themselves. They say it costs too much and makes people give up private insurance; the goal instead should be universal health care through a mix of public and private coverage.

Beyond identity and ideology, the contest is about Democrats yearning for a 2020 version of Barack Obama 2008, candidate who both unifies and electrifies the party. In 2008 Obama was the moderate candidate, not nearly as liberal as Hillary and John Edwards on, for example, health care. His personality, his inspirational oratory and the historic promise of his candidacy generated the excitement, not issues.

Is there a candidate this time who can energize progressives, mobilize millennials and minorities, and reassure moderates – in the primaries and in November? That’s what the next 10 months is about. And it will happen fast. By this time next year, Iowa, New Hampshire and Nevada will be over, South Carolina will be upon us and the first Super Tuesday, which includes North Carolina (and California), will coming up.

Just about every day between now and then, Trump will remind us what’s at stake. Last week there was his unhinged, nearly incoherent 50-minute Rose Garden rant on The Wall and the world. There’s the heavy-handed interference, obstruction and thuggishness toward law enforcement that make Dick Nixon look like Micky Mouse. There’s the drip, drip, drip of evidence that Trump is either in cahoots with Putin or Putin has his hooks in him. There’s the President of the United States saying he doesn’t care what our intelligence agencies say, he believes Putin. There are the reckless attacks on the media that incite violence against reporters and camera people. And there are ugly, nasty, angry tweets fired off at even the most inconsequential of targets, like a late-night TV comedy skit.

America can’t take four more years of this. Democrats must not blow it.