Walking around the House of Commons, you don't have to go very far to find an unhappy Conservative MP. David Cameron may have become Prime Minister, ending 13 years of Labour rule, but Tory MPs feel like passengers rather than crew on the coalition government's journey. The Conservative leadership is struggling to connect with a parliamentary party that feels underpaid, is threatened by a major review of constituency boundaries and isn't getting to see implemented the Conservative manifesto that it waited all those years for.

Given the coalition's radicalism, complaints about the ideological direction may seem odd. But, to understand the unhappy Tory MP, you need to distinguish between three different kinds of policy.

First, there are the policies of necessity – notably spending cuts – which nearly every Conservative MP supports but knows aren't popular. Second, there are the major, liberalising reforms of this government: greater school choice, making work pay, decentralising power. These are supported by the core of the Conservative Party, often very enthusiastically. But it's the third set of policies that best explains MPs' restlessness.

Agenda bending

I call them "mainstream Conservative" policies. They include a tough approach to crime, investment in defence, repatriation of powers from Europe and support for the family. They are the policies that motivate the Tory grass roots to raise money for their party and to stuff leaflets through letter boxes on wet Saturdays. They are the policies that most distinguish the average Conservative from the average Lib Dem or Labour activist. And you may have noticed they are barely part of this government's agenda. They are the policies that Nick Clegg has vetoed. As midterm unpopularity reaches record depths, as I predict it will, Cameron won't be able to reach for the mainstream policy toolkit for measures to sweeten the mood of his party.

The Conservative Parliamentary Party understands the compromises of coalition government but it worries that Cameron doesn't seem to share its frustration at them. He seems almost too content in the company of Liberal Democrats. Is the amity tactical or a testament to something deeper?

Conservative MPs want to see a plan for a majority Conservative government at the next election. Where, they wonder, is the proper inquest into the Tories' disappointing general election performance? Why, before Christmas, did Conservative cabinet ministers hold secret discussions on how they might help the Liberal Democrat candidate to win the Oldham East and Saddleworth by-election? Why are senior Tories, close to the leadership, permitted to brief newspapers about the desirability of an ongoing Con-Lib pact?

My own fear is that Team Cameron has drawn the wrong lessons from May 2010. Rather than blaming the agreement to hold the pre-election leaders' debates, or the wobbly Tory message for the English "striving classes", the small circle around the Conservative leader believes that it may be impossible for the Conservative Party to achieve victory at any election. They are particularly depressed by Scotland where, in four successive general elections, the Tories have won either just one or no seats at all.

No big decisions about tactics at the next election should be taken until we know the outcome of the referendum on the Alternative Vote (AV), which is to be held in May. Clegg wants to abolish first-past-the-post because he wants the Liberal Democrats to become the permanent power-brokers in British politics. It is why he went into the coalition negotiations ready to drop his party's tuition fees pledge – and much else besides – but with electoral reform as non-negotiable. Post-election trades between politicians would become the norm, not the exception, if AV passes. Politicians will have institutionalised the freedom to wriggle out of manifesto promises.

If AV is to be defeated, an anti-Clegg message probably needs to be central for the Conservatives. A model is the near-defeat of the Maastricht Treaty in France in 1992. Maastricht was rejected by many French people not because they had turned against the European project, but because President Mitterrand was hated. Opponents of AV need to turn the campaign into a referendum on the broken promises and horse-trading of coalition politics. An all-out attack on Clegg's screeching U-turn on tuition fees may be the best chance of keeping first-past-the-post but will Cameron sanction a campaign that is so hostile to his deputy?

Cameron agreed to the referendum in controversial circumstances. There is a suspicion that he conceded more than he needed to in the fog of the coalition negotiations. Now, in the eyes of his own party, he has an opportunity to put things right. Entering the electoral reform debate in unequivocal terms is his best early opportunity to demonstrate that he wants to implement mainstream, rather than just liberal, Conservative policies. He needs to campaign aggressively for keeping first-past-the-post and its ability to oust unpopular governments. He should also help to ensure that the "No" campaign is well-funded.

Grass-roots manoeuvre

Until now, Cameron has given the impression that his cure for internal party unhappiness is to invite Tory MPs for a glass of wine and a handful of Twiglets at a Downing Street reception. If he is to survive midterm unpopularity, he needs to do much more to raise his party's morale.

A chairman in tune with the party's grass roots would help – unlike the incumbent, Sayeeda Warsi. He also needs an additional parliamentary private secretary, someone who can connect him to the intake of 2010. They account for half of the parliamentary party and are already rebelling against his government in unprecedented numbers. Setting out a vision of a low-tax, pro-family Britain would be useful. Mainstream Conservatism may be impossible to achieve in this government but Cameron should show that it is still his ambition.

Ultimately, the fortunes of this government depend on the economy. If the UK is growing strongly by the time of the next election, it would be a brave pundit who would bet against a second term for Cameron. The task for the Prime Minister is to keep his party together in the difficult years between then and now.

Tim Montgomerie is editor of ConservativeHome.