What issue will matter most to American voters when they choose their next president? A recent Quinnipiac poll of likely voters appears to give a clear answer: the economy.

In a survey conducted last week, 24 per cent of respondents said that it was the most important issue to them when it came deciding which presidential candidate to support. The next most popular response was law and order (17 per cent), then the coronavirus and racial inequality (both 13 per cent).

However, as you might expect, there’s a substantial partisan gap in the responses. The economy is a top issue for 39 per cent of registered Republicans and 7 per cent of registered Democrats. The coronavirus comes top among Democrats, with 24 per cent compared to just 2 per cent among Republicans. If you look at the top issue by preferred presidential candidate, the difference is even clearer: there is no overlap whatsoever in the top four answers for Biden voters and the top four answers for Trump voters.

A few things make these numbers difficult to parse. The first is the relationship between the issues in this most unusual election year. Law and order and racial inequality certainly aren’t two sides of the same coin, but given the ongoing focus on police shootings of black Americans and the sometimes violent protest and unrest that has followed, they are unavoidably intertwined.

The same is true of the economy and the pandemic. In a political climate that has oversimplified the debate into lives versus jobs, to say your priority is the economy is, in many cases, to take a view on the best course of action in response to coronavirus. If you say the pandemic matters more, you see the hunkering down versus opening up calculation differently.

However, even this fuller picture misses what is really going on. Looking at what voters say they care about in 2020, I wonder if the way we’re accustomed to talking about how voters’ preferences translate into support for a candidate isn’t out of date. The assumption has generally been that a voter comes into election season with a set of issues they care about, assesses the claims, records and promises made by the candidates on those issues and votes accordingly. But such an approach is difficult to square with the chasm dividing Trump and Biden supporters on what matters most in 2020.

A far simpler explanation is that political affiliation is more like sports fandom than we would like to admit. Trump voters say they care about the economy and law and order while Biden supporters are worried about the pandemic and racial injustice for the same reason Manchester United supporters wear red and Manchester City supporters wear blue.

This hunch is backed up by a 2017 experiment by two political scientists at Brigham Young University found that Republicans voters were considerably more likely to support various liberal policies if they were told that Trump also supported them.

Here, you might argue, there is evidence of a more benign dynamic at play, trust in a political leader rather than blind partisanship. But I’m afraid I’m more cynical.

Consider the Financial Times/Peterson poll that has been tracking economic sentiment in the United States over the last 12 months. Asking voters whether they are better off in the years since Trump’s election, the survey finds a clear and consistent partisan split in how voters assess their own financial well-being. This month’s poll, for example, finds that 51 per cent of Democrats and 7 per cent of Republicans believe they are financially worse off since Mr Trump became president. Sixty-two per cent of Republicans and 13 per cent of Democrats say they are better off.

The inspiration for the FT poll is the question Ronald Reagan famously put to the American people in a 1980 presidential debate: Are you better off than you were four years ago? The answer was evidently no given that he defeated the incumbent, Jimmy Carter, in a landslide.

On Tuesday evening, Trump and Biden will meet in the first of three debates. The moderator, Fox News anchor Chris Wallace, has announced the topics: the candidates’ records, the supreme court, the pandemic, the economy, “race and violence in the cities” and “the integrity of the election.

Underpinning the idea of such an event is the platonic ideal of an undecided voter, earnestly weighing up the two candidates’ solutions to the problems of the day. The reality has never been that straightforward. But what does debate look like when voters can no longer agree on what those problems are? We’ll find out on Tuesday.