US midterm elections 2018 poll tracker: Who will win the Congress?

On November 6, America will go to the polls to elect members for each of the 435 House seats and 35 of the 100 Senate seats in Congress.

Donald Trump and the Republicans will hope to maintain their majority in both houses during the midterm elections, but with the Democrats having a healthy lead in the polls, it is believed that they have a decent chance of taking the House of Representatives.

A Democrat victory in either chamber would grant powers to open investigations into President Trump, so the stakes are high.

The latest polling and forecasts indicate that Donald Trump and the Republicans could hold onto both houses, although the House of Representatives looks the more likely to fall to the Democrats.

But the Republican president, who has faced tough weeks after his former campaign chairman Paul Manafort was found guilty of eight charges in his fraud trial, is reportedly planning 40 days of campaigning for the elections, and so the polls are likely to move further before election day.

General ballot between Republicans and Democrats

The latest polls show that the Democrats are around eight percentage points ahead of the Republicans, standing at an average of 47.1 per cent compared to the Republicans’ 40 per cent.

This is an average of the last eight polls, and has indicated a consistent lead for the Democrats on a national level.

While the Democrats are ahead in the general ballot, both the House of Representatives and the Senate are decided by a series of local elections, which means that the Republicans may still hold both houses.

The Democrats need 24 seats to flip the House of Representatives, and two to flip the Senate. But to make matters harder, the Democrats are defending 26 of the 35 seats up for election in the Senate this time.

House of Representatives forecast: Democrats knocking on the door

Of the 435 seats up for re-election in the House of Representatives, the Democrats need to flip 24 seats - something that should be within reach for the party.

The latest forecast, from the Cook Report, has the Democrats on a likely 205 seats and the Republicans on 199.

This means that the remaining 31 "toss-up" seats, which are too close to call, will be incredibly important for the outcome of the election.

Senate forecast: A tough Republican nut to crack

Only needing two seats to take the Senate, it would at first seem that the Democrats should be able to take control.

But there is an issue with this: Of the 35 seats up for election, 26 are currently defended by the Democrats. That means that the Democrats need to claim two seats from the remaining eight Republican-defended seats.

According to the Cook Report forecast, this seems unlikely, as there are only 45 seats that are marked as "leaning" Democrat or stronger.

To claim a majority, the party would have to pick up a further six seats that are either toss-ups or leaning towards the Republicans

Key seats to watch

In the 2016 presidential election, Trump won big in rural and working class communities. This helped him flip - albeit with small margins - traditionally Democrat states in the rust belt, including Wisconsin and Michigan. 

If the Democrats are to have hope of taking the House of Representatives from the Republicans, they need to ensure that they retain seats in these areas, before moving onto Republican territory in others.

A series of both Republican and Democrat seats are currently classed as a "toss-up" by the Cook Report, indicating that there could be turnovers for both parts in the mid terms.

The Republicans will hope to hold onto their under siege seats in places like Tennessee and West Virginia, while making inroads in Democrat areas that Trump claimed with huge majorites in the 2016 presidential election.

Seats in Indiana and North Dakota are among those places where the Republicans will hope that Trump's base will help them flip seats. 

Does President Trump's approval rating matter?

Donald Trump's approval ratings are at relatively healthy and stable levels as the mid-terms according to The Telegraph's poll tracker.

The tracker, which takes an average of the last eight polls, puts Trump's approval rating on 41 per cent in mid-September. 

While this level is quite high for Trump, it is relatively low for sitting presidents - and this is important, as presidential approval ratings are a good indicator of net losses at mid term elections. 

Only two presidents - Truman (1946 and 1950), and Bush (2006) - had a lower approval rating than Trump when going into their respective mid term elections. All three of these ended up losing over 28 seats in the House of Representatives and over five in the Senate.

The Telegraph's poll tracker takes an average of the last eight polls in order to take a  full picture of the broad movements in the polling environment and not put too much weight on individual polls. Polls used are nationally representative with adequate sample sizes.