United States —
On Tuesday, Americans will vote in what some people are calling “the most important election ever”. Donald Trump is not up for election, but both sides say the election is about him.
In 2016, Mr. Trump surprised much of the world when he was elected president of the United States. Since that time, he has taken the country in unexpected directions. Even members of Mr. Trump’s own Republican Party have been surprised and shocked by his decisions.

(Source: The White House, via Wikimedia Commons.)
But, despite their surprise, Republican politicians have supported Mr. Trump. The Republicans control Congress – they have the most seats in the Senate and in the House of Representatives. With this support, Mr. Trump has been able to do pretty much what he wants.
Presidents are elected every four years, but members of the House of Representatives are elected every two years, and senators are elected every six years. That means that at “midterm” – half way through a president’s time in office – the country gets a chance to vote for many members of Congress and about 34 governors. This election is often seen as a “report card” for the president.

This map shows the 33 Senate seats that are being decided.
(Source: WikimediaCommons.org.)
People think that if the country likes what the president is doing, many members of the president’s party will be elected. But if people are upset about the President’s leadership, the president’s party could lose the elections.
Right now, many people think Democrats may take control of the House of Representatives. It seems less likely that they will win in the Senate. If the Democrats do take control of either the House or Senate, it will make life more difficult for Mr. Trump.

(Source: Lorie Shaull, via Wikimedia Commons.)
Controlling both the White House and Congress has made it easy for Mr. Trump and the Republicans to make huge changes over the last two years. It also made it easier for Mr. Trump to avoid hard questions about whether he did things during the 2016 election that may have been against the law. That would change if Democrats controlled some or all of Congress.
In this election, the skin color and background of the people running has gotten more attention than usual. More women and non-whites are running than ever before.

(Source: The Circus (YouTube), via Wikimedia Commons.)
Over 25% of the people running for Congress or governor are women, and over 20% are people of color. Many states may soon have political leaders with very different backgrounds from the white men they’ve had in the past.*
Both Mr. Trump and ex-president Barack Obama have been traveling around the country, working to help members of their party get elected.

This picture of Mr. Obama speaking is from 2010.
(Source: Neon Tommy, via Wikimedia Commons.)
Mr. Trump and the Republicans have been warning people about immigrants (people trying to come to the US from other countries). The Republicans think if people are worried about immigrants, they will be more likely to vote for Republicans.
Democrats say it is important to stop Mr. Trump from doing the things he is doing. They worry that if Mr. Trump and the Republicans are in complete control for two more years, it will be very bad for the country and the world.
*The New York Times says that even though only 1/3 of the people in the US are white men, they make up 69% of the governors and members of Congress.