There’s an old West Indian saying that goes, “Hard ears that don’t hear, by and by will feel.” It’s not irrational to be concerned that this proverb will be proven true three years from now.

The 2020 Presidential election will be here before too long, and if the Democratic Party goes into the general election divided–if the party cannot unify behind whoever becomes Trump’s challenger, whether that challenger is a bona fide progressive or a supposed centrist–Trump will unquestionably become a two-term President. If that prospect frightens you, it should.

It will not matter if the economy has slowed down by November 3, 2020. It will not matter if Mr. Trump has mired us in an unwinnable war or two. It will not matter if Trump has broken key promises to members of his base. And it certainly won’t matter if Trump continues fondling his ego in public, as he did in his speech to the CIA yesterday. All Trump needs is a broken and divided Democratic Party–a party unable to harness the momentum generated by yesterday’s historic Women’s Marches across the country–to do it again.

It will be horrifying if a progressive secures the Democratic nomination, only to receive tepid support from members of the party who have problems with populism. It will be equally horrifying if a supposed centrist secures the Democratic nomination, only to be regarded with scorn by those who backed a undisputed progressive rival.

A unified Democratic Party could be an unstoppable political force; unity between the party’s left and “middle” would be the GOP’s worst nightmare. Conversely, when Democrats take up arms against one another, Republicans always prosper.

Imagine what would happen to this country if a 2020 Democratic nominee proved unable to truly unify the party. Today is the 34th anniversary of the Roe v. Wade ruling, which liberated American women. If a Democratic nominee failed to unify the party and thus came up short against Trump, the 45th President would have a clear path towards establishing an anti-Roe majority on the Supreme Court (assuming Republicans were still in control of the Senate after the 2020 Congressional elections). By the time Trump left office in 2025, the Supreme Court would be largely comprised of jurists whose interpretation of the Constitution would take us back to the right days of Lochner v. New York.

Imagine what two terms of Trump would do to women’s rights, to unions and workers, to the climate, to education, to civil rights, to health care, voting rights. Imagine the worst…and realize that it will happen if the 2020 Democratic nominee is sabotaged by squabbling.

Will we bear witness to another destructive fight between factions in the Democratic Party? Will we bear witness to an obsession with scrutinizing whether an allegedly “centrist” Democratic nominee took one nickel in campaign contributions from Wall Street, or, conversely, nonsensical navel-gazing over whether a strongly progressive Democratic nominee is “too far left” to win a general election? Will we bear witness to the opposite of unity?

If Democrats never forget that sick feeling they had in their stomachs when Trump was declared the winner of the Electoral College–the sick feeling that motivated the concerned citizens who took to the streets yesterday–they’ll remain focused on the most important goal going into the 2020 Presidential election. If they allow petty feuding to obscure that goal, Trump will have four more years to radically remake this country. For Democrats, it’s either war against Trump or war against each other. The former is winnable. The latter is a quagmire.

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D. R. Tucker is a Massachusetts-based journalist who has served as the weekend contributor for the Washington Monthly since May 2014. He has also written for the Huffington Post, the Washington Spectator, the Metrowest Daily News, investigative journalist Brad Friedman's Brad Blog and environmental journalist Peter Sinclair's Climate Crocks.