Election 2015: What to watch out for in the BBC debate
The stage is set for the BBC's live election debate, hosted by David Dimbleby, featuring the five main opposition parties in the UK general election campaign. Here is a guide to the contest including what we might hear from the panellists.
Where can I watch it?
Who is taking part?
From left to right on the podium, the leaders taking part will be Labour's Ed Miliband, Plaid Cymru's Leanne Wood, the Green Party's Natalie Bennett, the SNP's Nicola Sturgeon and UKIP's Nigel Farage. David Dimbleby will host the programme.
How will it work?
Each of the leaders will be invited to make a short opening statement before five questions from the audience. They will be given a minute to answer before 10 minutes of free debate. At the end, each leader will deliver a short closing statement.
What might the leaders talk about?
The first live debate, featuring seven leaders, gave us a clue as to the parties' favoured attack lines, although they may adopt different approaches in the absence of David Cameron and Nick Clegg. Here's what you might hear from each leader:
Mr Miliband is the only leader taking part who could realistically be prime minister after the election. He may portray the vote on 7 May as a choice between Labour and the Conservatives, seeking to set out his vision and contrasting it with David Cameron's. Because the Conservative leader is not taking part, it will give Mr Miliband the chance to attack his policies without reply. He could confront the SNP given that polls suggest Labour could lose most of its seats in Scotland on 7 May, and attempt to counter the threat from UKIP to Labour seats in England.
Because Mr Miliband is the most high-profile participant, he could face the most criticism from the other leaders. The four he will be debating against have portrayed themselves as anti-establishment in some way or another.
The Plaid Cymru leader focused her attention firmly on Wales during the last national TV election debate. She has previously called for Wales to be given equal treatment with Scotland in terms of funding and powers.
Along with Ms Sturgeon and Ms Bennett, Ms Wood has pledged to work to combat austerity policies after the election, so it is likely that will come up.
At the Green Party manifesto launch, Ms Bennett identified stopping privatisation in the NHS, increasing the minimum wage to £10 per hour and a plan to help the two million children growing up in cold homes as key priorities. She may bring these up at the debate.
At the seven-way election debate she was keen to tell the audience there was an "alternative" to making the poor and disadvantaged pay for the mistakes of bankers. Expect more on that theme.
Her party only stands in Scotland, but Ms Sturgeon deliberately pitched to the whole of the UK during the last debate. It's likely she will do the same again, promising to fight for "progressive" politics at Westminster after 7 May.
One issue she may bring up with Mr Miliband is whether there will be cuts in Scotland under a Labour government. Earlier this week, shadow chancellor Ed Balls said Scotland would not be exempt from cuts after the election, a day after Scottish Labour leader Jim Murphy said the party would not need to make "further cuts to achieve our spending rules" in the next Parliament.
Ms Sturgeon could also be questioned by Mr Miliband on her backing for full fiscal autonomy for Scotland; the Institute for Fiscal Studies has said Scotland would face a £7.6bn budget deficit under the proposals and the Labour leader may push Ms Sturgeon on how that would be plugged.
The UKIP leader is the only member of the panel who wants to leave the EU and has made the issue a central plank of his manifesto. He is likely to bring it up during the debate and may attack Mr Miliband for his party's refusal to back a referendum on membership of the EU in the next Parliament. Immigration is also key to the UKIP campaign and Mr Farage is likely to argue it needs to be brought down, something he says can only be properly achieved if the UK leaves the EU.
At his manifesto launch on Wednesday, the UKIP leader also fired a broadside at the Barnett Formula, which decides the amount of money allocated to the Scottish government for spending. That issue could come up and if it does, expect some fiery exchanges between Mr Farage and Ms Sturgeon.
Why aren't David Cameron and Nick Clegg taking part?
That's open to interpretation.
The final schedule of pre-election debates came after weeks of wrangling between the political parties and the broadcasters over the timing and line-up. Mr Cameron rejected the first proposal because it did not include the Greens. The revised version was published last month.
The BBC said the broadcasters had "worked hard" to offer audiences "the best possible combination of programmes to help them engage with the election, to inform them about the issues and to scrutinise the politicians". All sides in the negotiations had made "compromises", the corporation said, adding that "ensuring due impartiality is not only a priority, but an obligation".
What about the DUP?
The Democratic Unionist Party has said its exclusion from the schedule is "outrageous". Its leadership had previously threatened legal action over its omission, because the DUP has more MPs than four of the parties invited to take part. Rejecting the DUP's appeal, the BBC Trust said its impartiality was crucial and network TV debates could not include "just one" party from Northern Ireland.
The debate will be followed at 21:30 BST by a half-hour analysis programme featuring reaction from the Conservatives, the Liberal Democrats and the DUP.