The Conservatives are going into December’s general election as odds-on favourites not only to win but to secure a majority.

Senior Tories today put their chances of forming a government at between 50-50 and two-thirds, with bookmakers giving a win a 90 per cent probability.

Boris Johnson’s party is priced at 4/5 to get an overall majority, which will be crucial if he is to get his Brexit deal through parliament.

As election expert Sir John Curtis noted, “this is not an election that Labour have to win to stop Brexit, but it is an election that they and the other opposition parties simply need to deny the Conservatives a majority.”

Getting there could be a monumental task for the Prime Minister.

Rallying his troops today he said he is prepared to contest a “tough” general election battle, cautioning against any complacency.

But what factors could derail his campaign? We take a look below.

Starting from a losing position

Johnson is about to attempt what Theresa May couldn’t do in 2017. But here’s the rub; he’s starting from a losing position. The Conservatives are currently well short of the majority they need to govern effectively, and with several of the old guard stepping down or defecting to other parties they have a lot of lost ground to recover. That could be tricky in the current climate, and with just 0.13 per cent of the British population voting Boris we still don’t have a good gauge of what the public feels about our controversial PM.

Losing Scottish seats to SNP and Remain seats to Lib Dems

Labour could be the least of the Conservative’s worries at this election. Early indications suggest Nicola Sturgeon has her eyes on a total wipe-out in Scotland, while Jo Swinson says the Lib Dems could win “hundreds of seats”. As ambitious as that sounds Sir John believes they may be on to something. “We could have more than 100 MPs that do not belong to either of the other two parties”, he said, which could diminish any chance of a Tory majority.

Gaining Labour seats they’ve never won

Johnson spent a lot of time in the north when he was first appointed Prime Minister and there’s a good reason why. Leave-voting seats in areas such as Doncaster and Rotherham will be firmly on the Conservative’s radar as they look to steal ground in Labour heartlands. But many of these places have never elected a Tory MP and he will have a fight on his hands to convince them otherwise, particularly if a Brexit Party alternative stands in his way.

The Farage factor

Tory MPs have been pleading with the Brexit Party not to run candidates in their seats at the general election, according to the party’s chair, Richard Tice. The party, spearheaded by Nigel Farage, has so far vetted 600 candidates for a general election and there is a presumption it is aiming to stand in all 650 seats. Even if they don’t return any MPs they could seriously water down the Conservative’s share of the vote, particularly in northern areas.

A potential NHS winter crisis

One of the major concerns held among senior Tory MPs is that a potential NHS winter crisis could derail their campaign entirely. Many of them have been warned that this winter’s NHS crisis was expected to be the worst in decades and that they were worried the government was struggling to properly prepare. This is the sort of thing that could quickly take the focus of the campaign away from Brexit onto terrain more friendly to Corbyn, one MP told Buzzfeed News.