The polls will decide who will take the majority in the House of Representatives and the Senate.
The stakes are high for US President Donald Trump, as should the Democrats gain a majority on Tuesday he will lose some of the power he currently has.
Critics of the President are hoping this will happen and that subsequently passing bills will be made more difficult.
The midterm elections are so called as they take place in the middle of the current president’s term in office.
Donald Trump was elected in 2016, so has been in power for two years.
Who will win the US midterms?
For some, voting began early as some states allow early voting.
However, the results will not be known until after everyone has had the chance to go to the polls next week.
Opinion polls are predicting a close race between the Democrats and Republicans, and a recent poll by YouGov of 1,296 US adults saw 47 percent in favour of the Democrats and 43 percent in favour of Republicans.
Also impacting the voters is Donald Trump’s approval rating.
In a separate poll of 1,000 US adults, YouGov found that only 43 percent approved of the President.
His reaction to issues such as the migrant caravan approaching the US from Mexico has influenced voters who say that immigration is a main topic of interest during this election.
There has also been a number of high profile violent incidents in recent days.
Last week a deadly attack on a Pennsylvania synagogue left 11 people dead.
Trump spoke of the attack at a Farmers of America convention in Indianapolis.
He said: “This wicked act of mass murder is pure evil — hard to believe, and frankly something that is unimaginable.
“This was an anti-Semitic act.
”You wouldn’t think this would be possible in this day and age, but we just don’t seem to learn from the past.”
He added: ”There must be no tolerance for anti-Semitism in America or for any form of religious or racial hatred or prejudice.”
As well as this, a number of high profile critics of the President were last week sent suspicious packages, some of which contained improvised explosive devices.
Luckily these were intercepted and did not cause any damage.
The President’s reaction via Twitter to the suspicious mail provoked upset as he blamed the packages for slowing down votes for his party rather than focusing on the threat they posed.
He tweeted: “Republicans are doing so well in early voting, and at the polls, and now this ‘Bomb’ stuff happens and the momentum greatly slows – news not talking politics. Very unfortunate, what is going on. Republicans, go out and vote!”