US midterms polls: Who will win control of Congress?

The final polls of the midterm elections are out and can help give us an answer to the question on everyone's mind - who will win?

Indications are that the Republican Party is on the verge of taking back control of the US House of Representatives for the first time in four years.

The upper chamber of Congress, the Senate, remains too close to call. There are more paths to Republican victory in the Senate than there are for Democrats, who have held the barest of majorities there for the past two years.

Understanding how it could unfold in both chambers is just a question of maths.

In the House, Republicans need to flip only five seats out of the 435 in the chamber to have a majority.

According to the Cook Political Report, which analyses the competitiveness of races based on polling data and underlying election dynamics, Republicans are favoured in 212 seats. They would have to win just six of the 35 races listed as toss-ups to control a majority.

Ten of those seats are already held by Republicans, so victory in this scenario wouldn't require ousting a single Democratic incumbent. It would take a significant polling error, in the aggregate, for Democrats to maintain the House speaker's gavel. Most professional forecasts at the moment predict Republicans will win between 20 and 30 seats, which would give them a comfortable operating majority.

The 100-seat Senate is somewhat simpler to understand. Only 35 seats are up for election this year, and there are only a handful of closely contested races.

Democratic incumbents are defending Nevada, Arizona, Georgia and New Hampshire. Republicans seek to hold open Senate seats in Ohio and Pennsylvania. All of the contests are within or near the margin of error according to most major polls. A net change of one seat toward the Republicans will swing the chamber to them.

Given that Democrats are trying to protect more seats than Republicans, there are simply more ways for Democrats to lose the Senate than to win it. That gives the Republicans the upper hand, albeit by the narrowest of margins. The Senate and the House don't always track the same way, however. In 2018, Democrats flipped the House but lost seats in the US Senate.

Taken in its totality, however, it appears likely that Republicans will control at least one chamber of Congress once the dust settles on these midterm elections.

After two years of unified Democratic control in Washington, the power dynamic in the nation's capital is poised to shift. That would have some very real implications American politics for the next two years.