US midterm elections- a simple guide

Two years after Joe Biden was elected US president, voters return to the polls on 8 November.

The midterm elections - so called because they fall halfway through a president's term - take place every four years.

Americans are represented in government by 535 lawmakers, known as members of Congress.

Congress is made up of two chambers - the Senate and the House of Representatives. The two work together to make laws.

The Senate is the 100-strong upper chamber. Each US state - regardless of size - sends two representatives. These senators are elected for six-year terms. Every two years a third of the Senate faces re-election.

The House of Representatives (often referred to as "the House") has 435 members. Each one represents a particular district in their state and serves a two year term. All seats are up for election.

Currently, all members of Congress align with the Democratic Party or the Republican Party.

The Democrats control both chambers, but by very slim majorities.

So far, this has made it easier for President Biden, a Democrat, to get things done.

But if the Republican Party gains control of either or both chambers, it will have the power to thwart the president's plans.

Republicans need to win five extra seats to take back the majority in the House this November.

It is even closer in the Senate, where the seats are evenly split between both parties at present. At present, the Democrats have control because Vice President Kamala Harris has the casting vote in any tie.

The Republicans only need to win one extra seat to gain control in November.

Primary elections to determine who will contest the general election for each party will take place around the country between May and September.

Historically, the party that holds the White House has tended to suffer losses in the midterms.

That is likely to undermine support for Democratic candidates.

Conservative Democrats - not Republicans - have blocked several major proposals, including "Build Back Better", the president's trillion-dollar package for social programmes and climate action.

A heavy defeat in the midterms will make it even harder for the president to introduce new laws.

Several Republicans have also expressed interest in taking a closer look at the the Biden administration's affairs.

Public health measures, particularly mask rules, have further deepened these divisions.

Divided control of Washington is likely to mean more drama and hostility.

Once the midterms election ends, all eyes will turn to the 2024 presidential election.

It could be a repeat of 2020 - both Presidents Biden and Trump say they plan to run again.

But various first-time contenders are expected to throw their hats in the ring too.

As well as the elections for Congress on 8 November, 36 out of 50 state governors are up for election. Of those 36, 20 are Republican.

When presidential campaigns get under way, governors play an outsized role supporting their party's candidates and overseeing their state's elections.

A divided Washington and a crop of new governors could have a major effect on presidential campaigning in 2023 and 2024.