Three scenarios for how the US midterm results could unfold

Three ways the US midterm results could play out

After months of campaigning and billions of dollars spent on the US midterms, election day has finally arrived.

The latest public opinion surveys suggest Democrats have the edge - but polls have not always been dependable, and this year could still produce some surprises.

Broadly speaking, though, there are three possible outcomes once Americans cast their votes.

Here is a look at what those outcomes could be, what early clues may emerge as results come in, and what it could mean for the country.

If history is any indication, midterm elections usually favour the party out of power.

Add to that what polls indicate is a historically unpopular president, a war with Iran that has pushed up consumer costs, and several controversial policies - such as aggressive immigration enforcement and support for data centre construction - and the conditions are in place for a so-called electoral wave.

In this first scenario, that wave is exactly what happens.

Democrats could not only seize control of the House of Representatives, but also go well beyond the 218 seats required for a majority. They might win not just the dozen or so races election analysts consider too close to call, but also flip some seats in more reliably conservative territory.

In the Senate, this would mean Democrats winning all or most of the current toss-up races, including some in traditionally conservative states. There would be at least one striking victory in a place that has not elected a Democrat in a generation, Texas, or in nearly a century in the case of Kansas.

If that happened, Democrats would not merely take the Senate - they would do so with one or two seats to spare. That could avoid any drama over a possible legal challenge by Republicans in Alaska, where a judge dismissed a Trump administration lawsuit over two Dan Sullivans being on the ballot.

Democrats might achieve this by driving up turnout among their voters and winning independents by wide margins. That would reverse Trump's 2024 gains with Hispanic voters and young men. Some Republican voters might also back Democrats or simply stay home.

Such an outcome would amount to a sharp rebuke for Trump and his Republican Party, setting up two years of conflict between a newly energised Democratic Party firmly in control of legislative power and a president who rarely backs down from a fight.

Early signs as the results come in:

If Democrats hold targeted House races in Florida and win some Republican districts in North Carolina, Michigan, New York, Virginia and Kentucky. If they flip the Senate seat in South Carolina, it will be a strong night for Democrats.

Maybe the polls will not be completely wrong, but not completely right either.

In this scenario, Democrats could still win enough of the easier House races to secure a majority, but not a large one.

That would mean Democratic leaders in the chamber would regularly have to negotiate with members on the left and in the centre to make sure they have enough votes to pass legislation.

In the Senate, Democrats would only flip one or two seats - North Carolina, for example, looks all but certain - but the races in the conservative heartland would be out of reach.

Perhaps they cannot unseat the stubbornly resilient Republican Senator Susan Collins in Maine, or left-wing candidate Abdul El-Sayed cannot keep Michigan in the Democratic column.

Maybe the duel over the Dan Sullivans is enough to sink Democratic candidate Mary Peltola in Alaska.

For this "Democratic trickle" scenario to happen, the strong Democratic turnout seen in early voting would need to be matched by a Republican surge on election day.

Trump's efforts to energise his base in Republican red states could help his party avoid the worst-case outcome. The races that were at or near the margin of error in polls could produce mixed results for both sides.

The outcome would be a divided Congress - and that is a recipe for political gridlock.

Early signs as the results come in:

If Florida remains comfortably Republican across the board. If Democrats gain some House seats in places like Virginia and Pennsylvania, but Republican incumbents in more secure political territory around the country avoid being swept away in a deluge.

This scenario has Republicans holding on to both chambers of Congress.

For that to happen, the polls - which have previously underestimated Trump's support - would need to be wrong, and the toss-up races would need to mostly break for Republicans.

Not only would Republican voters have to turn out in unexpectedly strong numbers, but independent and Hispanic voters who appeared to have turned against Trump's policies would also have to break his way in the end.

In this scenario, control of the House, far from being a sure thing for Democrats, could come down to California and its extended days-long process of counting mail-in ballots.

In the end, Republicans might narrowly secure an overall majority, helped in part by efforts to draw more favourable congressional district lines in places like Texas, Florida and North Carolina.

It could also be that Republicans win all the Senate races in conservative states and also flip Michigan, a seat Democrats held going into the vote.

Even if Republicans do not hold North Carolina or win in Democratic-controlled Minnesota or New Hampshire - races just on the edge of competitiveness in this year's elections - they may at least force Democratic candidates to sweat.

If that happens, Trump might on Wednesday morning claim a renewed electoral mandate and push ahead with his domestic and foreign policy agenda with the continued backing of a Republican Congress.

Early signs as the results come in:

If Senators Ashley Moody in Florida and Jon Husted in Ohio cruise to re-election. If Republicans hold their own in House races in Pennsylvania and Virginia, and they flip current Democratic seats in North Carolina, Ohio and Florida.