Tories are very vulnerable ahead of this week’s elections

By Gideon Skinner, head of politics at Ipsos Mori

As David Cameron said last week on the Today programme, it's time for the government to "raise their game". By quite how much is made clear by Ipsos Mori's latest political monitor for the Evening Standard. Approval ratings for David Cameron and the government have fallen to their lowest point, after weeks of negative reaction to the Budget, the handling of Abu Qatada's deportation, and internal divisions over what the coalition parties stand for.

If we look underneath the topline figures, we find some interesting stories about what might be driving these changes. After a long time in which Ed Miliband has been criticised for his lukewarm ratings amongst Labour voters, there are now some signs that it's the Conservatives who are feeling some chill winds from their own base.

Just before the Budget, two-thirds of Conservative supporters were happy with the way the government was running the country, and an impressive 81% were satisfied with David Cameron, much better than Ed Miliband or Nick Clegg were doing among their own supporters.

But one month on, while Labour and Lib Dem voters have barely changed in their assessment of the government's performance, satisfaction among Conservatives has fallen sixteen points to 50%. This is only just higher than the 43% who are dissatisfied.

At the same time, satisfaction with David Cameron has fallen from 81% to 68% among Conservatives, while dissatisfaction has doubled (although, to be fair, this is still higher than Miliband and Clegg get from their voters, which perhaps highlights for them that they still have more to do).

A lot of the government's troubles this month have been laid at the feet of the Budget, and while Conservative supporters are more positive about it than other voters — as we would expect — there are signs that the government's reputation for economic credibility has taken a hit.

In particular, George Osborne's ratings as chancellor have fallen from his honeymoon period to the worst Ipsos Mori has seen for over 20 years, and much of this has been among his own supporters.

Back in December, fully three-quarters of Conservative voters were satisfied with his performance. One month on from the Budget, this has fallen to just half, while the proportion of Conservatives unhappy with him has doubled to 41%.

Now these are just changes from one poll, and we shouldn't claim too much until we've seen whether these are the start of a new trend or just the response to a bad month. And it's true that the change in voting intentions has been less dramatic. But nonetheless, as my colleague Roger Mortimore has pointed out, at this stage of a parliament it can be just as useful to look at approval ratings as voting intention.

Votes that will count, though, will be the results of this week's May local elections, and especially for the London mayor. These could have a big impact on party morale, and play an important role in determining whether the narrative of Conservative difficulties continues or is seen as a blip. With that in mind, this cooling off among the Conservative's own supporters seems particularly badly timed.

The big story since the election has been the holding up of the Conservative vote, while Labour has benefited at the expense of the Liberal Democrats. But if the Conservatives continue to be hit where it hurts — in David Cameron's prime ministerial qualities, and in their reputation for competence and credibility — this story could change.