How political structures allow both parties to claim victory

Despite worries that low approval ratings for US President Donald Trump would cost Republicans control of both chambers of Congress, Democrats were facing an uphill battle.

With vote counting continuing, Republicans look likely to keep and even increase their slim Senate majority as they lose their grip on the House of Representatives.

The result is broadly in line with what many analysts projected, but makes for a confusing picture – how are the Democrats on course to soundly rout the Republicans in the House and lose seats to them in the upper chamber? To put it simply, different rules govern elections for the two chambers.

The 100 members making up the US Senate serve six-year terms and the elections for those seats are staggered.

This means that only one third of seats are up for re-election during midterms.

So why did the Democrats lose these seats? Because they were defending more vulnerable Senate positions this time.

Some of those seats, won in 2012 when former president Barack Obama was ending his first term, were in conservative parts of the country such as Indiana and North Dakota.

In these typically “red states”, Democratic incumbents lost their re-election bids.

But for the House of Representatives, with 435 members, all seats are generally up for grabs every two years. Those numbers were significantly more favourable to Democrats, enabling them to make gains.

Peter Yacobucci, an associate professor of political science at Buffalo State University, explained the origin of the rules.

“United States voting rules are an artefact of the creation of the country,” he said, referring to the US Constitution, which established the House of Representatives and the Senate.

The rules and mixture of term lengths were designed as a system of checks and balances, ensuring equitable representation among different populations in the US and for elections to take place at different times to smooth out the bumps and troughs of the prevailing political mood of the day.

There was some hope among Democrats that an energised electorate angry at Mr Trump would allow the party to beat expectations and take both legislative chambers. Many spun it as a referendum on his two years in office.

But Mr Yacobucci said that, even with an increase in Democratic turnout, midterm voters in general tend to skew towards the conservative, somewhat blunting the impact.

While the remaining states are still working their way through boxes of ballot papers and the final tally is still to be called, broadly speaking the overall result looks clear and Mr Trump’s next two years will look very different from the first two.