Congress has two chambers: the House of Representatives (435 members) and the Senate (100 members).

In the House, each state receives seats based on its population size. 

Each state is guaranteed at least 1 seat, making votes in a low-population state like Wyoming relatively more influential.

The entire House is re-elected every 2 years.

This happens at the same time as the presidential election, plus an extra time halfway through a President’s term (midterms).

• The President’s party has lost House seats in 40 of 43 midterms since 1842.

In the Senate, each state gets 2 seats, regardless of size.

Each Senator serves a 6-year term, with 1/3 of the Senate re-elected every 2 years.

Since the 1850s, one of 2 has parties won the congressional elections: the Democrats or the Republicans.

They have changed their ideology and policies over time.

• In theory, any party can win, but (1) it is expensive and (2) the seats are not allocated proportionally, so a majority is needed for representation.

The President is elected indirectly through a system called the Electoral College.

• Each state gets a number of electors equal to how many seats the state has in the Senate and the House, combined.

• A popular vote in each state decides who the state’s electors will vote for.

This was designed in 1787 as a compromise between election by Congress and a direct popular vote.

5 times in history the elected President would have lost in a direct popular vote.

• In 2016, Donald Trump won the electoral vote 304-227 while Hillary Clinton won the popular vote by 2%, or 3 million votes.

State and local elections (for governors and lawmakers) run on their own cycles, meaning there are many local elections every year.

Federalism, explained

In a federation, power is shared between the central and regional governments, unlike a unitary state (where the centre holds all power) or a confederation (where the states do).

• In the UK, for example, local power is given by the centre and can theoretically be removed.

The Constitution gives the federal government specific (enumerated) powers such as defence and foreign policy, and reserves the rest to the states, including education, health and criminal law.

Both levels of government can also tax, borrow and run courts.

The Supremacy Clause: where federal and state law conflict, federal law wins.

The Commerce Clause gives Congress the power to regulate interstate trade.

It has been used broadly since the 1930s to cover most economic activity.

• In 1942, the Supreme Court ruled that even wheat grown for personal use on one farm fell under federal regulation, because in total such activity affects the interstate market.

Presidential power has grown over the past century, with the largest expansions in the 1930s, during the Cold War and after the 2001 terror attacks on the US.

Presidents now use executive orders, emergency powers and executive agreements to act without new law passed by Congress.

Party loyalty now regularly overrides institutional loyalty: members of the President’s party in Congress defend the party’s interest more than their chamber's powers.

The federal government attaches conditions to the money it gives to the states to influence policy.

Federalism produces policy differences between states: cannabis, abortion, the death penalty and minimum wages all vary by state, in what is called the ‘laboratories of democracy’.