To adapt a line from Huey Lewis, I want a new party — one that won’t make me sick.

I have written so often (and so recently) about the ways Donald Trump’s G.O.P. makes me sick that I won’t repeat myself here. It’s enough to say that when the president calls for four elected members of Congress to “go back” to their supposed countries of origin and neither the Senate majority leader nor the House minority leader can bring themselves to condemn it, you know you are dealing with a party that lacks brain, heart, spine, and vital parts further south.

Then I come to the Democrats.

I liked some of what I heard this week from the Democratic debates. I liked hearing a candidate call attention to the fact that if we simply withdraw our forces from Afghanistan, we will invite a humanitarian catastrophe “that will startle and frighten every man, woman and child in this country.” I liked hearing another candidate acknowledge that the only realistic way to get to net zero carbon emissions by 2050 is to “innovate our way out of this problem.” I liked the candidate who scolded Trump for meeting with Kim Jong-un and giving the dictator “a huge win.”

The only problem: The three candidates I just mentioned — Colorado’s John Hickenlooper, Maryland’s John Delaney and Ohio’s Tim Ryan — are polling at 2.0 percent, collectively. Their chances of winning the Democratic nomination are about as great as mine are of becoming executive director of Greenpeace.

Experienced Democratic hands think the party will have a giant political problem if it nominates a candidate too far to the left. That’s probable but not certain. Ruy Teixeira of the Center for American Progress has made a highly plausible case that Democrats should not expect to win the election simply through a base mobilization effort, at least not when it comes to the states that count. Democrats did well in last year’s midterms thanks to vote switchers electing moderate candidates like Utah’s Ben McAdams. They did considerably less well with turnout campaigns that failed to elect progressives like Florida’s Andrew Gillum.

Then again, experienced Republican hands never imagined in the summer of 2015 that someone as extreme as Donald Trump could win the G.O.P. nomination, much less the election, by mobilizing hidden G.O.P. voters. And here we are. The only solid electoral lesson from 2016 is that nobody knows nuttin’ about nuttin’.

So it’s hardly out of the question that Bernie Sanders, Elizabeth Warren or Kamala Harris could beat Trump. The problem is that too many of them advocate terrible policies, ruinous schemes, discredited notions and crackpot ideas.

I admire Pete Buttigieg, but his proposal to add six more justices to the Supreme Court is a bridge too far even for Ruth Bader Ginsburg. It’s also an invitation to reckless institutional revision by whoever happens to be in power — which, at some point, will be another president in the mold of Trump.

I admire the Democrats for seeking humane solutions for the border crisis. But decriminalizing border crossings (favored, to one degree or another, by Sanders, Warren, Harris, Buttigieg, Julián Castro, Cory Booker and Kirsten Gillibrand) would turn a humanitarian disgrace into a full-scale catastrophe, while also inviting a massive populist blowback.

I admire anyone who attempts to save us from our Rube Goldberg health care system. But advocates of Medicare for All have no realistic answer to the question of how hospitals are supposed to stay in business when two-thirds of them already lose money on Medicare inpatient services.

I do not admire anyone embracing the bad idea of free college. The surest way to strip nearly anything of its value is to make it free.

I do not admire the Democrats relentless demonization of American corporations, which as of 2017 employ a plurality of the U.S. work force. When Warren accuses U.S. multinationals of having “no patriotism” and “no loyalty to America,” does it not occur to her that she’s taking a cheap shot at millions of potential Democratic voters, who might not enjoy hearing that they, too, are deplorable?

I do not admire anyone who, whether through political opportunism or astonishing naiveté, embraces the Green New Deal. It is to climate change what an old-fashioned phlebotomy would be to pneumonia: a bad cure for a problem that can only be solved through rapid economic growth (that makes environmental action in the developing world affordable) and dramatic technological innovation (that makes climate mitigation effective and democratically palatable).

I particularly do not admire anyone advocating slavery reparations — the ultimate Pandora’s box even if one leaves aside the practicalities of figuring out who owes what to whom. For starters: If reparations really are owed, shouldn’t they first be paid — at an incalculable financial cost — to Native Americans?

All of this is worse than farcical. It’s tragic. It will make the Trump campaign’s job of selling the president as the non-insane option in next year’s election shamefully easy. And it will do nothing to address our core political crisis: a democracy in which the center bends toward the fringe rather than the fringe bending toward the center.

I realize some readers will discount this column as unwanted advice from a non-Democrat. But I want Trump to lose next year as much as anyone. The party on view in Detroit was not close to being up to its historic responsibility of defeating him and governing responsibly in his place.

– Bret L. Stephens has been an Opinion columnist with The New York Times since April 2017.