Andrew Grice: PM eager to answer the 'man or mouse' challenge

The test for David Cameron in his first full-scale reshuffle was to prove whether he was "a man or a mouse". It was set last week by Tim Yeo, the former Environment Minister, who challenged the Prime Minister to have the courage to drop his previous opposition to a third runway at Heathrow Airport.

Mr Cameron passed the Heathrow test by shunting Justine Greening out of the Department for Transport after only 10 months. Yesterday's Cabinet shake-up was also a wider "man or mouse" test for the PM, who has looked increasingly weak in the face of mounting criticism from his rebellious MPs.

There was plenty for the Tory traditionalists to cheer in what will be seen as a lurch to the right.

Nick Clegg does not have a veto over Tory appointments. He would have preferred Kenneth Clarke (dubbed "the sixth Lib Dem Cabinet minister") to stay at the Ministry of Justice and will not be overjoyed that Owen Paterson, a right-wing climate change sceptic who opposes wind farms, is taking over the environment brief.

Despite the constraints imposed by coalition, the Prime Minister was exerting his authority. "He hopes it will galvanise the troops," one Cameron ally said last night. It will certainly please the Tory right, which has been urging the PM to stand up to Mr Clegg.

Aides insist Mr Cameron promoted the best people for a new phase of delivering reform. But they don't deny a tilt to the right.

The reshuffle may stabilise his party for a while, but there could be trouble ahead. Stroppy Tory backbenchers will expect the shift to the right in personnel to be matched by a parallel shift in policies. But if the newly appointed Tory ministers try to push through a raft of right-wing measures they will face opposition from the Lib Dems, who do have a veto on policy.

The danger for Mr Cameron is that yesterday's shake-up is seen as his departure from his modernising project. If the Conservatives are seen as the "nasty party" again, that could open up a gap in the market for the Lib Dems, who will target "soft Tories" after losing many progressive voters. Mr Cameron may need to appeal to his own party now, but in 2015 he will need to appeal to the whole country.