Rishi Sunak is taking a huge gamble with his political career as he gets set to call a general election for July 4.

The Conservatives are well behind in the polls, with Labour expected to win a thumping majority, and it's been reported that a number of his MPs have attempted to call a vote of no confidence in response.

It appears though that Mr Sunak believes things are as good as they're going to get for his premiership, and is gambling on the six week campaign allowing him to narrow the gap.

Here are some of the other big political gambles - some of which paid off and some of which resolutely did not.

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Theresa May, 2017

Operating with a small majority of 17, Ms May struggled to make any headway with Brexit due to internal divisions in her party.

She aimed to rectify that by calling a general election, with polls showing the Tories had a 21 point lead over Jeremy Corbyn's Labour party.

Instead Ms May lost 13 seats as Labour recorded its biggest vote share since 2001 and left her reliant on the DUP to get anything passed in the house.

After two years of varying degrees of deadlock she was forced to stand down.

David Cameron, 2015

A gamble which paid off in the short-term but not in the long was Mr Cameron pledging a referendum on EU membership in the Conservative manifesto for the 2015 election.

The Tory leader was hoping to see of the threat of UKIP by delivering a vote on Brexit and it worked, his party gaining 24 seats and achieving the majority they couldn't five years previously.

The Herald:

It proved something of a poisoned chalice though, with Mr Cameron campaigning for remain and immediately resigning when the vote was lost.

Gordon Brown, 2010

This is probably an example of a Prime Minister being afraid to pull the trigger and it costing him.

Mr Brown was initially very popular when he took over from Tony Blair, with speculation in 2007 that he would call a snap election and polls predicting that he'd win.

He opted not to, and with a global recession hitting the following year the conditions were never as favourable again.

When the election did eventually take place in 2010 it resulted in a hung parliament but the Conservatives emerged as the largest party and haven't been out of government since.

SNP, 1979

Amid a period of political unrest, Conservative leader Margaret Thatcher tabled a motion of no confidence in the Labour government, led at the time by James Callaghan.

The SNP opted to vote in favour - two of their 11 MPs abstained - after the failure of the first referendum on devolution and the government fell by just one vote.

Mr Callaghan has said since that his government would have fallen eventually anyway, but at the subsequent election Ms Thatcher won a majority and the SNP lost all but two of their MPs.

The Scotland act was repealed and devolution wouldn't happen until 1997, and it wouldn't be until 2015 that the SNP returned double figures to Westminster.

Harold Wilson, 1974

The second election to be held in that year after Harold Wilson initially failed to win a majority in the first vote in February.

The Labour leader went to the country again in October, winning a majority of three seats.