Election 2020 Democrats Donors

A view of the White House in Washington, Wednesday, Jan. 23, 2019. Multiple Democrats have already entered the 2020 presidential race. (AP Photo/Susan Walsh)

You would think the far-left wing of the Democratic Party would have learned some humility in the wake of midterm elections in which candidates endorsed by Sen. Bernie Sanders, I-Vt., were mowed down in primaries and more centrist candidates rolled up wins, taking back the House majority and grabbing a batch of governorships. You'd be wrong.

Jonathan Cowan and Matt Bennett of the centrist Third Way take exception with an assertion from New York Mayor Bill de Blasio, D, that "centrists got us nowhere." Well, except the House majority, Cowan and Bennett point out, and all that goes with it (e.g. oversight hearings, passage of voting reform).

Those fretful that a Democratic nominee easily labeled as a wide-eyed radical could hand the 2020 election to President Trump know that ideological purity makes for bad politics. It's no fluke that Trump spent some of his State of the Union address raising the boogeyman of socialism, Venezuela-style.

Amy Walter of the Cook Political Report observes, "Privately, lots of Democratic insiders also fear that the only thing standing between Democratic victory in 2020 and another Trump term is a nominee who scratches the itch of the liberal base but can't appeal to the moderate middle."

Democratic contenders in 2020 would be wise to adopt a few basic rules. These should prevent them from going over the left edge of the party while maintaining comity in a party that will need to unify after a spirited primary.

First, they shouldn't have fights with de Blasio or anyone else over labels and ideological one-upmanship. (Socialists bad! No, centrists are losers!) This is entirely unproductive, indeed meaningless, when no one defines their terms. Democrats would be smart to debate policy ideas (let others label them) and make the case as to why they are better suited to beating Trump and then governing effectively.

Second, don't sign on to bumper stickers. (Medicare for All! The Green New Deal!) This only empowers the far left to set the terms of the debate and exempts the far left from explaining and defending flawed policies. Why not come up with their own ideas, ones designed to unify the party and appeal to non-Democrats? You don't have to sign on to pie-in-the-sky bills that will never get a vote, even in the House, to stake out support for solutions to climate change, worker dislocation and more.

As to the Green New Deal, Jonathan Chait explains: "On the policy, the Green New Deal simply outlines ambitious targets for carbon reductions, without delving into specifics as to how the targets will be met. In place of detail it offers optimism."

Candidates set themselves up for trouble when they take seriously something just about everyone knows isn't serious. ("America won't get 100 percent of its power from zero-emissions sources within a decade, either, another audacious Green New Deal goal," writes Michael Grunwald. "And we're not going to upgrade the energy efficiency of every single building in the country, as the resolution proposes. If we were getting all our energy from zero-emissions sources, it wouldn't even make sense to try.")

Third, those who aren't on the fringe of the party need to reject the tag that they are "mushy" moderates. Bold moderation and clear, fact-based reforms with wide support that get at the heart of our biggest problems shouldn't be a bad thing. The goals that virtually everyone in the field has set -- expanding health care, combating global warming, equalizing educational opportunities, passing comprehensive immigration reform, enacting gun safety laws -- are very popular. What's not popular is the most extreme, unrealistic incarnation of these goals.

Democrats who have entered the 2020 race aren't running to be mayor of New York or a senator from Vermont. They're running for the nomination of a party that has to appeal to a big, diverse and contentious country. Democratic primary voters seem to understand this, even if some party activists do not. Democratic contenders best not crawl out so far on a limb that they won't be able to scamper back when Election Day 2020 rolls around.

Jennifer Rubin is a columnist with The Washington Post.