Cameron's three goals in Birmingham

"The eurozone is starting to look like a giant game of dominos – and unless the rest of the world gets its act together, it too could soon be forced to start playing. This story is highly relevant to Britain: the state is collecting 40 per cent or so of GDP in revenues and spending 52 per cent (on OECD stats) – as anybody who has ever had to run a household, a company or any kind of budget knows, such a large overdraft is unsustainable. Countries aren’t immune to the laws of economics."

- Allister Heath, City AM

This is not a good time to experiment with a hung parliament: Tonight's economy debate takes place against the backdrop of a gathering storm across Europe. Greece is already engulfed. Portugal is teetering. Spain is vulnerable. "The growing crisis," writes Iain Martin, "is at root about large debts and the markets demanding that states start taking serious action." Now is not the time for Britain to undertake a risky experiment in coalition or minority government. Cameron can quote plenty of business leaders and business polls to back his case. The Director-General of the Institute of Directors said yesterday: "The risk is that there will be no agreement on the nature of public spending reductions, and that on this key issue a coalition or minority government will be paralysed." Cameron doesn't need to set out detailed measures but he needs to look the nation in the eye tonight and say that he will take the tough decisions so that Britain can look forward to better times and that he has a growth plan to deliver it. He needs to come out of the debate as the straight-talker. People are ready for some candour.

He has an open goal in front of him on immigration: Mrs Duffy expressed the view of 75% of the British people and she was called a bigot. The Liberal Democrats have unworkable policies on immigration. The Tories have good policies. Cameron needs to set them out clearly and directly.

He needs to paint Nick Clegg as evasive on what he'd do in the event of a hung parliament: This is how I'd do it:

"Let me give you one other guarantee tonight. I will not keep Gordon Brown in power. I do not question Mr Brown’s sincerity but he and the Labour government have done enormous damage to Britain. Every baby born today carries £23,000 of debt because of Labour. Because of Mr Brown’s changes to the regulation of the City, banks were not inspected properly. Most unforgivably, our troops were sent to war without proper equipment. So, let me be clear: I will end the Labour years. I will not keep Mr Brown or any of his colleagues in power under any circumstances. Nick Clegg will not give you that guarantee and because he won’t give you that guarantee you do not know what a Liberal Democrat vote might mean. Your choice is real change with the Conservatives or a risk of more of the same. And that is why I am asking for your vote."

Tim Montgomerie