The 2018 US midterm elections are most Americans' first opportunity to pass judgment on Donald Trump since his election two years ago.

The US holds congressional elections every two years. At each election the whole of the House of Representatives and one third of the 100-member Senate are elected. The representatives thus serve a two-year term, and the senators six years.

These elections are known as midterms when they fall outside the four-year presidential election cycle. Being in the middle of the presidential term, they are usually understood to be at least partially a reaction to the president's performance so far, and usually see the president's party losing seats.

Donald Trump's Republicans - red in the maps and charts, and often called the GOP, or "grand old party" - went into the election campaign controlling both houses of Congress. The opposition Democrats - in blue above - were hoping for a "blue wave" that would put them in a position to moderate and sometimes block Trump's agenda.

These live results come from the Associated Press. Some other information comes from the US Congress. The Guardian race ratings are derived from other polling organisations and our own research.