When American voters go to the polls on Tuesday, they will be voting not only in a multitude of specific races, but in what feel like two separate elections. The first is a largely traditional version of the midterms: a referendum on the incumbent (helping to explain why Joe Biden has been keeping a relatively low profile, given his approval ratings) and on the economy. In a cost of living crisis, it may not be surprising that 92% of Republicans see the economy as very important, with predictable issues of crime and immigration following behind.

But among Democrats, only 65% see the economy as very important – while 80% cite the future of democracy, 79% cite healthcare and 75% abortion. This is the second and very different contest. It is a “struggle for the very soul of America”, as Mr Biden warned on Wednesday, and a battle over people’s fundamental rights – to control their own bodies, and to have free and fair elections. The context is the storming of the Capitol on 6 January 2021; the vicious attack on Nancy Pelosi’s husband by a man who told police he had planned to kidnap the House speaker and break her kneecaps if she “lied” to him; and the supreme court’s overturning of Roe v Wade. The latter led to a surge in registrations, and more than half of registered voters still say abortion will be very important in determining their choice. But Republican candidates who have realised the unpopularity of their extreme views are now muddying their message, as even some voters who define themselves as “pro-life” balk at total bans.

The question is how much ground Democrats lose. Polls suggest Republicans will almost certainly take the House and are favoured to take the Senate. Whether they prove more accurate than in recent years is critical to an outcome which will help to determine everything from US support for Ukraine to the 2024 presidential race. A triumph for the Republicans will mean a hobbled administration, facing legislative stagnation, hostile committees and investigations on matters such as Hunter Biden’s business dealings.

But this is also a defining moment in the defence of democracy. Thanks to Donald Trump’s lies, amplified by hard-right media outlets like Fox News, grassroots Republicans believe, entirely wrongly, that the 2020 election was unfair or outright stolen – a belief not dented even when his own officials testified to his defeat. The consequences have included political violence; the danger of more is clear. But this “big lie” is also playing out in midterm races.

The electoral system is already warped by years of gerrymandering, as the growing gap between the Democrats’ share of the popular vote and actual political power demonstrates (though the House race appears fairer than in recent contests). Now it is under fresh threat from outright election deniers who question or reject Mr Trump’s defeat and won’t commit to accepting defeat themselves. If the former president runs in 2024 – as he says he “very, very, very probably” will do – key election officials may not resist his attempts to overturn his defeat as they did in 2020. In Arizona, all but one of the Republican candidates for Congress, governor, attorney general and secretary of state have questioned the 2020 result.

The very act of casting a vote in the midterms may help to preserve or imperil democracy. But because very protracted counts will probably be followed by legal challenges and threats, winning means not just persuading voters, but ensuring that their choices are upheld. An increasingly polarised electorate may move even further apart. It is unsurprising that there are two contests when there are, increasingly, two different Americas, who cannot even agree on the facts, still less what they mean for the nation.