What are they?
In the US half way through a presidents time in office an election is held to, effectively, judge their performance and success in carrying out their political manifesto (a set of policies laid out during the election campaign that the candidate aims to implement/follow through their time in office) In nearly every midterm election- except from Bush, Clinton and Obama who gained seats- presidents tend to loose seats or even a majority in one or both chambers in Congress (the House of Representatives and/or the Senate) Or if the electorate have a widespread dislike to the president and they way they conduct themselves this vote can lead to the removal of them from office. The consequences of loosing a majority (over 50%) of the seats in one or more chambers is that it restricts their ability to influence their members to vote of their policies or amendments (changes to the constitution) because the opposing party- which is currently the Democrats- will vote against Republican agenda.
Why are they used?
They give the electorate (people who are legally allowed to vote) a chance to reign back the presidents power (if they think he/she has exceed it) or show a disproval of their attempts to achieve the policies voted for in their manifesto. Moreover, they are seen to enhance democracy as the electorate have the ability to remove or have a say in restricting a presidents power if they believe they are acting unconstitutionally or not focusing enough on achieving their manifesto policies. Also they are a good way of providing checks on a presidents power, making sure that they are heavily focused on achieving their policies (as that is what the electorate are expecting of them- laid out during their campaign) otherwise they risk loosing seats or their place in office in the midterms.
Moreover, as it is a form of political participation it is crucial that people who are eligible to vote turnout and vote, otherwise the politics becomes favoured in more direction (normally favouring older demographics as they turnout the most to vote, and therefore presidents will try to accommodate them as much as they can in their manifesto so that they vote for them). Many famous actors or just regular American’s have created videos online encouraging younger people to vote or the president won’t do anything for them. (see links below for more detail)
The ‘Save the Day’ campaign encouraging people to vote with Robert Downey Jr., Scarlett Johansson, Julianne Moore etc.: https://www.youtube.com/watch?v=nRp1CK_X_Yw
When are they?
They were held on November 6th 2018 and will dictate whether President Trump will remain president, remain president with a majority in Congress or remain president with fewer seats and a lost majority.
Already, according to the Telegraph, there has been a massive early turnout with 38.8 million people casting their votes early, as opposed to 27.4 million in 2014.
It is predicted that the Democrats will achieve a simple majority totalling a forecasted 210 seats in comparison to 195 seats for the Republicans in the House of Representatives, in comparison to the Republicans currently holding the majority; and then the Republicans maintaining their majority in the Senate, very marginally with the Democrats only loosing out on 2 to 3 seats in comparison.