This article originally appeared in the Guardian on September 19th, 2019.

One of the clearest takeaways from the Democratic presidential debate in Houston last week is that the party has a Joe Biden problem. As the frontrunner, Biden has blocked other moderate candidates from making a credible case for the nomination, while his amorphous and uninspiring centrism makes it more likely that the eventual Democratic nominee may end up going too far left to defeat Donald Trump in 2020.

In Houston, Biden was more focused and forceful than he had been in previous debates – although that was a low bar to clear. He was at his most effective when critiquing the Medicare for All plan, chiding Bernie Sanders for the astronomically high cost of the proposal and Elizabeth Warren for her unwillingness to admit it would impose any financial burdens on middle-class taxpayers.

Biden missed numerous examples to play up his deep experience in lawmaking and foreign policy, which his supporters tout as the antidote to Trump’s chaotic and disruptive governing approach. But he did call attention to the fact that he was the only candidate to have defeated the NRA in the legislative arena, when he secured passage of the 1993 Brady bill requiring background checks for firearms purchases.

To the extent that Biden made an affirmative case for his candidacy during the debate, it was that he’s running to restore the status quo that prevailed during the eight years that he was Barack Obama’s vice-president. Democrats still revere the former president, who in 2018 registered a 97% favorable rating from party members. At the Houston debates, some of the most progressive candidates went out of their way to praise Obama – a significant shift from the previous debates, when they treated his legacy with something approaching disdain.

“I’m for Barack,” Biden proclaimed at the debate, and his partnership with Obama is one of his greatest advantages with Democratic voters.

But Trump’s presidency has accelerated the radicalization of most Democratic activists, if not the majority of Democratic voters. Obama himself may be off-limits for criticism, but Biden has become the target for progressives who are disappointed with the Obama-Biden administration, which they consider to have been insufficiently “woke” on race and immigration, excessively accommodating toward corporate interests on trade and taxation, and naive in believing Republicans would cooperate with them on matters like healthcare and climate change.

Biden struggles to respond to such charges because, in typical centrist fashion, he wants everyone to like him. He will not make a robust defense of his centrism because he’s unwilling to denounce progressive excesses, other than to say that this or that policy is too expensive or won’t pass Congress. There haven’t been any Sister Souljah moments in Biden’s campaign, and there probably won’t be.

During the debate, he had no good answer to an accusatory question about the high number of deportations during the Obama presidency. That’s because, at a time when many progressives appear to think there should be no restrictions on immigration whatsoever, he couldn’t openly defend the border enforcement policies he once supported. Rather than restating the Obama administration’s argument that the Trans-Pacific Partnership trade deal would have significantly improved global labor and environmental standards, he meekly agreed that unions and environmental activists should be included in future trade negotiations. Confronted with his 40-year-old quote rejecting reparations for African Americans, he couldn’t reply that reparations are still a widely unpopular and unworkable idea, so instead he served up an indigestible word stew larded with random thoughts about social workers, record players and the dictator of Venezuela.

Biden’s centrist program, at least as he presented it during the debate, boils down to little more than a more incremental and cost-conscious version of the progressives’ plans. The moderate wing of the Democratic party may be relieved that Biden so far hasn’t been sucked into endorsing the progressives’ identity politics, but his articulation of what he wants to accomplish has so far been anything but inspiring.

If Biden continues in the same dispiriting vein for the next several months, he will continue to overshadow more interesting proponents of Democratic moderation such as Amy Klobuchar and Michael Bennet (who failed to make the debate). Eventually, in the view of many Washington political observers, he will lose much of his popular support and fade from contention. In that case, many Democratic strategists worry that the remaining Democratic candidates will continue to try to outflank each other on the left, to the extent that the eventual candidate turns off the moderate majority of Americans and Trump wins re-election.

If Biden is to avoid that fate, he might reflect on the difference between centrism and moderation captured in the idea of “trimming”, a nautical concept turned to political metaphor by the 17th-century English statesman George Savile, the Earl of Halifax. When the boat you’re sailing is being blown off course, sitting in the dead center of the boat isn’t going to get you where you want to go; you may have to lean hard to one side of the boat or another to counteract the force of the wind and waves and keep you moving in the right direction. Moderation, unlike centrism, can be dynamic and innovative rather than inert and imitative.

If Biden wants to invigorate his campaign, he should try to reorient the Democratic conversation around bold moderate ideas that aren’t just cautious versions of the progressives’ plans. When defending free trade and the free market, he should think harder than he did as vice-president about how to more equitably distribute their benefits. (And if Sanders persists in calling countries like Denmark socialist, Biden should point out that their robust social safety net enables more unfettered capitalist competition than we have here.)

Biden should sound the alarm about the opioid epidemic that led to nearly 140,000 Americans dying of overdoses during the past two years – a horrifying fact that went completely unmentioned in the Houston debate. He could call for a tax on the bloated financial sector, which could be used to address the disproportionate loss of home equity wealth suffered by minorities in the financial crisis.

While no Republican legislator will ever endorse the Green New Deal, Biden could emphasize his ability to persuade many of them of the need for a carbon tax to offset climate change – an idea that’s slowly gaining acceptance among Republicans. He could champion the carbon-capture technologies that most of the progressive candidates instinctively resist. And he might point out that ideologically moderate Democrats performed much better than progressives in the 2018 elections.

In the interest of full disclosure, I should add that as a registered Republican, I won’t be able to vote for any of the candidates in the 2020 Democratic presidential primaries. But as a political historian, I believe that few significant and enduring legislative achievements – from the New Deal to the civil rights legislation of the 1960s to Ronald Reagan’s pro-business reforms – have been passed without appealing to a critical mass of moderates in both parties.

And as an American citizen, I hope that the next president, whoever he or she is, will be bold enough to make the far-reaching reforms our society and economy and environment need, but also moderate enough to restore the social unity and functional government that we currently lack.

Geoffrey Kabaservice is the director of political studies at the Niskanen Center in Washington DC as well as the author of Rule and Ruin: The Downfall of Moderation and the Destruction of the Republican Party