Speculation is high that Gordon Brown will call a snap general election this autumn. But what are the prime minister's options?
Is there going to be a snap election?
Only one man can decide, and that is Gordon Brown. He is expected to spend the weekend looking at opinion polls - both those in the papers and those carried out by Labour - before announcing next week whether he will go to the country.
So, what do the polls suggest?
They seem to be getting more complicated. Polls following last week's Labour Party conference suggested Mr Brown had a substantial lead. But the first polls to emerge since David Cameron's speech to the Conservative conference this week put the two parties far closer, with the Guardian/ICM one placing them neck-and-neck. Polls following conferences are known to be volatile and difficult to read, making Mr Brown's decision even harder.
How short can an election campaign be?
Just over three weeks is the short answer. Of course, campaigns usually go on for longer - in 1997, John Major called an election eight weeks before polling day. But there is a minimum of 17 working days between the issuing of a writ to returning officers in each constituency - telling them to return an MP for the next Parliament - and the election itself. The prime minister can announce the election date on the same day as writ is issued.
What dates are seen as the favourites for Mr Brown to call an autumn election?
Political analysts say the most likely timing would be Thursday 1 or Thursday 8 November.
So, when would a 1 November contest have to be called?
An announcement would have to be made by Tuesday 9 October - a day after Parliament returns from the summer recess.
Why would this help Mr Brown?
It would give him time to make his planned statement on Iraq. The government will also announce the Comprehensive Spending Review - which sets government budgets for three years - and pre-Budget report on Tuesday. In addition, this timetable would avoid a potentially embarrassing Conservative-led Commons debate on the government's decision not to hold a European treaty referendum, which is scheduled for Wednesday 10 October.
And an election on 8 November?
This could be announced at any time up to Tuesday 16 October, giving the government an extra week to pass some remaining legislation.
Could Mr Brown go to the country any later in the autumn?
Another date sometimes mentioned is 15 November, which would allow Labour - and the other parties - more time to get campaigners in place and candidates selected. The final possible announcement date for this would be 23 October.
Why is this date seen as less likely?
It is also widely believed that, if the election is held further into November, the likely colder weather will reduce turnout among Labour voters.
When does Mr Brown have to call an election?
He has until May 2010 to do so, with Labour having won the last general election in 2005, under Tony Blair. A change of prime minister does not alter this, as the electorate votes for local MPs - rather than specifically for a party leader, as happens in presidential systems. But some commentators say that, as Mr Blair promised to serve a full term in government, Mr Brown lacks a full "mandate" and should call an election sooner rather than later.
Why does the election have to be on a Thursday?
It does not. The law only states that an election has to be held on a date that is not at the weekend, on a bank holiday or on a day "appointed for public thanksgiving and mourning".
There would need to be emergency legislation if, as has sometimes been reported, Mr Brown wants to hold an election on a Sunday. Thursday, though, is traditionally the polling day in the UK.
If an election is called, what happens to parliamentary business?
All outstanding legislation from the time that Parliament is dissolved falls. So any bills would then have to be reintroduced after the election.
And the parties?
Under the rules, a snap general election could give parties as little as six working days to select and nominate all their candidates. Currently hundreds of constituency parties and associations have not made their choice.