Isabel Hardman

How do the Conservatives make the Clacton by-election more difficult for Douglas Carswell? I hear from two extremely well-placed sources that the selection for the Tory candidate will be an open primary. Carswell himself bemoaned the demise of this selection method when he announced he was leaving the party to join Ukip, and party sources have been muttering for a few days that the authority of the new Ukip candidate is rather undermined by his decision to shunt the poor, bewildered local Ukip chap, Roger Lord, out of the way. Now sources tell me that the party will revive open primaries for this election to make it more difficult for Carswell.

If the Tories did want to really fight Douglas Carswell in the Clacton by-election, then Boris Johnson would have been a jolly good way of driving a steamroller over Ukip's chances of doing well. James explained at the weekend that when David Cameron reached the same conclusion and put the feelers out to the Mayor, word came back that Johnson felt Clacton was too far away. But today Johnson suggested that those feelers weren't particularly robust ones.

Nick Clegg had a stab at being René Magritte on the Today programme this morning, telling us that a disagreement between the two coalition parties over anti-terror measures that were sort-of announced yesterday was 'not some argument between two political parties'. It was clear from the way the Deputy Prime Minister described the additional measures for TPIMs that the Lib Dems accepted David Anderson's demand that the government do more, but that only the first option, the expansion of exclusion zones, is something that will wash. Relocation powers, the key power removed from control orders when the Coalition scrapped them, would prove far more controversial, even though the Tories are clearly happy to keep an open mind on introducing these if necessary.

The talks between the Lib Dems and the Conservatives on the anti-terror measures that David Cameron will unveil this afternoon have finally finished. There are a few more details to be thrashed out - crossing of Ts and dotting of Is rather than major policy decisions - but the two parties are basically there. That the talks have only broken up with just over an hour to go until the statement shows how contentious these measures have been in the Coalition. David Cameron's press conference, in which he set out the heightened threat, was partly a softening-up exercise to push the Lib Dems into accepting what the security and intelligence services had told him: that they needed to plug the 'gaps in Britain's armoury'.

What should worry David Cameron more, Douglas Carswell's defection to Ukip or reports that as many as 100 Tory MPs could go into the general election pledging to leave the European Union? The former is certainly more dramatic and promises plenty of humiliation over the next few months. But the latter could show the Prime Minister that he doesn't have as much time on European reform as he would like, and that he is still not trusted by a large contingent of his party. It is one thing for Better Off Out members such as Mark Reckless to pledge to campaign to leave, no matter what reforms David Cameron manages to secure.

It was not so much the announcements that David Cameron made in his press conference about the terror threat to the UK that were significant, but what he looks like he's going to have to announce on Monday. The Prime Minister confirmed that the threat level to the UK has been raised from 'substantial' to 'severe'. But he also said that on Monday he will be unveiling new measures to address 'gaps' in the UK's 'armoury': 'I said very clearly last week that there would be no knee-jerk reactions. We will respond calmly and with purpose. And we'll do so driven by the evidence and the importance of maintaining the liberty that is the hallmark of the society that we defend. But we have to listen carefully to the security and the intelligence officers who do so much every day to keep us safe.

Stuart Wheeler has just been boasting on Sky News that two more Conservative MPs are 'seriously considering' defecting to Ukip. Wheeler has been the broker in any potential defections, wining and dining potential converts before asking if they want a meeting with Nigel Farage. Not all of them have said yes to that second offer. It is, though, plausible that there are MPs who are still not rock solid in their decision to back the Tories all the way to the next election. The result of the Clacton by-election, how David Cameron plays the Europe question and how he manages the party over the next few months will determine whether they do go or not.

What will be the impact on the Conservative party of Douglas Carswell's defection? Even though there is some excitement this morning about other meetings that Ukip has held with Conservative MPs, it is worth pointing out that those meetings were firstly held a while ago, and secondly that a number of those MPs who did meet Stuart Wheeler decided not to meet Nigel Farage because that would have been a betrayal in itself of their party. Some did meet Farage, but decided not to make the leap. Carswell was one of those MPs who initially did not make that leap, so it is unwise to say that there will be no more defections. But when Coffee House spoke to most of those MPs yesterday, none of them had changed their mind as a result of this defection.