Do Democrats win by moving left? Or is moderation the key to victory?

For Americans who would resist President Trump’s re-election in 2020, the outcome hinges on the answer to this basic strategic question: will the Democrats risk losing to Trump by nominating a candidate whose ideas are too far to the left to appeal to the moderate majority of Americans? Or will Democrats risk losing to Trump by nominating a candidate whose ideas are insufficiently progressive to excite the Democratic base?

This basic question of moderation v progressivism was at the heart of the first of two Democratic debates in Detroit and doubtless will continue to be central throughout the rest of the primary process. By taking one side or another, Democratic voters will be making a choice not only for the candidate and the policies he or she will stand for, but also for how the campaign will be conducted and the underlying rationale for how political change can be accomplished.

The moderate/progressive split was on clear display in Tuesday’s debate. Senators Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts upheld the progressive side, while moderates were represented by Representative Tim Ryan of Ohio, the former representative John Delaney of Maryland, Senator Amy Klobuchar of Minnesota, Governor Steve Bullock of Montana and the former governor John Hickenlooper of Colorado. The former representative Beto O’Rourke of Texas and Mayor Pete Buttigieg of South Bend, Indiana to some extent tried to straddle both wings, while the spiritual guru Marianne Williamson occupied her own dimension but generally adhered to the progressive side.

Related: Who won the Democrats' debate? Our panelists' verdict

The debate was stacked against the moderates in the sense that Sanders and Warren are leading contenders for the nomination, polling around 15% in most polls, while the moderates struggle to reach 1%. Both Sanders and Warren had considerably more speaking time than any of their opponents, and the comparative insignificance of the moderates (in terms of polling, at any rate) meant that Sanders and Warren didn’t really have to engage deeply with their criticisms.

Nonetheless, the outline of the moderate/progressive split became clear over the course of the debate. The progressives believe that Democrats must dramatically restructure government, politics and the economy – what Warren referred to in the debate as “a corrupt, rigged system” that operates mainly in the interests of “the wealthy and well-connected” – in order to foster a more equitable society.

Sanders is an avowed socialist while Warren calls herself a “capitalist to my bones”, but both see large corporations and billionaires as malign forces driving corruption in Washington and inequality in society as a whole. Neither is calling for a government takeover of the means of production, but Sanders in the debate characterized the fossil fuel industry as “a criminal activity” and rejected the idea of healthcare as a business, while the Medicare for All plan that Sanders and Warren endorse would in effect nationalize the health insurance industry.

Both Sanders and Warren support decriminalizing the border and providing government health insurance to undocumented migrants. Both advocate large-scale government intervention to make public higher education free and forgive student loan debt. They support the Green New Deal, which calls for eliminating carbon emissions by 2030 as well as providing a federal jobs guarantee. They would pay for these plans in large part by imposing a tax on the wealthiest Americans.

The moderates in the debate did not refer to themselves as moderates or centrists, but rather presented themselves as pragmatic progressives. Some of the ideas they put forward would have been considered fairly radical in the recent past, including a public option for healthcare (giving people under age 65 the choice of buying into Medicare), direct government negotiation to lower prescription drug prices, universal pre-K education, and a plan to tax carbon emissions and return the revenues as a “dividend” to all households.

Unlike the progressives, however, the moderates took pains to emphasize that their programs were bold but “realistic”, meaning that they would be popular with the public as well as financially and legislatively feasible – as opposed to what Bullock characterized as “wishlist economics” and Delaney called “free everything”.

Delaney rejected Warren’s wealth tax as unworkable and probably unconstitutional, though he agreed that “wealthy Americans have to pay more” and called for raising the capital gains tax. Klobuchar criticized the idea of free college as a giveaway to wealthy Americans. The moderates rejected Medicare for All on the grounds that it would take away the private insurance that many Americans (including union members) value – and Hickenlooper added that none of the Democrats who won back control of the House by flipping Republican seats in the 2018 elections had supported the plan. As Delaney put it, “Democrats win when we run on real solutions, not impossible promises; when we run on things that are workable, not fairytale economics.”

To the progressives, that sounded like what Warren called “small ideas and spinelessness” – a cowardly avoidance of necessary structural change. Warren also scored one of the night’s most memorable lines by wondering aloud “why anybody goes to all the trouble of running for president of the United States just to talk about what we really can’t do and shouldn’t fight for”.

That was a low blow, given that Delaney and the other moderates do in fact advocate ambitious policies. They’re not standing for inaction, and their moderation is not mere incrementalism or acceptance of the status quo.

But the moderates, by and large, are concerned not only with practicality but also with restoring the sense of national unity shredded by Trump, while the progressives call for fighting fire with fire. While neither moderate nor progressive candidates have a clearly articulated view of how their proposals will become reality, moderates pay at least some heed to the possibilities for bipartisanship – not a word that Sanders or Warren uttered at the debate – and assembling broad coalitions of support.

Moderates, for example, want government to collaborate with business on projects such as rebuilding the nation’s infrastructure. They also see healthcare companies as part of an overall solution to the problems in that field; Delaney at one point charged that the progressives’ Medicare for All plan revealed “an anti-private sector strategy”.

Progressives, on the other hand, believe corporations are such self-serving, parasitic and unpatriotic entities that they have to be opposed at all turns, not just in the health and energy fields but almost across the board. Warren boasted: “I took on Wall Street, and CEOs, and their lobbyists, and their lawyers, and I beat them.” Sanders took pride in having voted against all trade agreements on the grounds that “if anybody here thinks that corporate America gives one damn about the average American worker, you’re mistaken. If they can save five cents by going to China, Mexico, or Vietnam, or anyplace else, that’s exactly what they will do.”

Trade agreements such as Nafta and the Trans-Pacific Partnership were, of course, negotiated during the administrations of Bill Clinton and Barack Obama, and part of what divides Democrats is the question of whether the achievements of those comparatively moderate presidencies are worth defending. In this week’s debates, Bullock hailed Obamacare as a legislative accomplishment decades in the making and worth building upon, while Delaney protested that Warren’s critique of TPP ignored that it did include strong environmental and labor standards. But Warren’s charge that “for decades, we have had a government that has been on the side of the rich and the powerful” certainly included the Clinton and Obama presidencies in her indictment.

Moderates also warn that many of the progressives’ ideas may appeal to Democratic activists but are unpopular with the general public. For example, roughly six in 10 Democrats favor giving health insurance to undocumented migrants, but overall, Americans oppose such a policy by a 59% to 38% margin. A Kaiser Family Foundation poll from earlier this year found that a majority of those surveyed approved the idea of Medicare for All, but support dropped precipitously when respondents were told that this would require eliminating private health insurance. Ryan, in pointing out the general unpopularity of those positions as well as the notion of decriminalizing the border, warned: “I quite frankly don’t think that that is an agenda that we can move forward on and win.”

Policy choices, for both moderates and progressives, relate to their overall electoral strategies. Moderates want to appeal to the suburban, college-educated voters who gave the Democrats the House majority in 2018, as well as to independent voters and disaffected Republicans. Progressives, on the other hand, put their hopes in what Sanders called “a campaign of energy and excitement and vision” that would boost grassroots turnout, particularly among young and minority voters. Progressives point out that if minorities had gone to the polls for Hillary Clinton in 2016 at the same rate as they had for Obama four years earlier, she would have won. Moderates counter that the same could be said of Clinton’s failure to attract Obama’s level of white working-class support.

Bullock, in Tuesday’s debate, insisted that “we do have to win back some of those places we lost” in 2016, “and get those Trump voters back if we are going to win”. Several of the moderates called for reaching out to voters in the “left behind” parts of the country. Klobuchar argued that “there are people that voted for Donald Trump before that aren’t racist, they just wanted a better shake in the economy” – a pointed rejection of the notion that the white working class is motivated more by racism than economic distress and thus can’t (and shouldn’t) be cultivated by Democrats.

Most of the moderates in Tuesday’s debate will not qualify for the next round of debates in September, and prospects for Democratic moderation will probably rise and fall with Joe Biden’s showing in the polls. Whoever emerges as the eventual nominee, it’s clear that Democrats are deeply divided and that the disagreements between moderates and progressives won’t be easily reconciled.

• 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