Say what you want about Britain's first-past-the-post electoral system, it does at least focus the attention.

Take our region, for example.

No matter how big a swing the Conservatives achieve, there are still only a handful of seats that are likely to change hands.

It is these 'weathervane' constituencies that will determine who forms the next government. And it is here that the parties will be concentrating both their efforts, and their limited funds.

Some have a particular significance. David Cameron speaks openly about the importance of Bolton and Bury to his party. Not only because they contain three marginal seats, but also because of the symbolic value of the Tories gaining a foothold in a Greater Manchester town.

Mr Cameron, who has invested a lot of effort winning hearts and minds in the urban north, wants a national mandate for change. He wants to be able to say he speaks for everyone. He needs the political map to show blue, as well as red and yellow, in places like ours.

But there are other constituencies in Greater Manchester which will have special significance this time, for all sorts of reasons.

Can the Liberal Democrats defend Cheadle against the Tories, and Withington and Rochdale against Labour? They will need to if Nick Clegg is to credibly claim his party is moving forward rather than stagnating. And will the anger over 'expensesgate' lead to seismic shifts in paces like Salford, or will it prove to be a storm in a (taxpayer-funded, bone-china) teacup?

Here, then, is my list of the top three constituencies to watch at the general election next year.

Bolton West - 2005: Ruth Kelly (Lab), Majority 2,064

A Labour seat since the Blair revolution of 1997 and held by the arch-Blairite, high-achieving Ms Kelly. It was not always thus; the seat was in Conservative hands between 1983-1997. In the 1950s it was a Liberal stronghold.

Ms Kelly is standing down this year. The Labour candidate will be Julie Hilling, a local activist who has lived in the constituency for two decades and rose through a trade union background.

Her Tory opponent is Susan Williams, the well-known former leader of Trafford council. Ms Williams, one of the faces of the successful 'no' campaign during the congestion-charge referendum, is in many ways Mr Cameron's ideal 'northern' candidate: straight-talking, pragmatic and moderate. But she is also a skilled politician, who opponents underestimate at their peril.

The Liberal Democrats are also standing a woman candidate - Jackie Pearcey, a widely-respected councillor in Manchester who will run a strong campaign. Expect the Tories to pour resources into the constituency, with 'big beasts' from the shadow cabinet likely to be stalking the streets in the weeks and months to come. It's one they will feel they will have to win to have any chance of forming the next government.

2005 result: Lab 17,239, Con 15,175, LD 7,241

Current odds: Con 2/7, Lab 5/2, LD 50/1

Bury North - 2005: David Chaytor (Lab), Majority: 2,926

How can the Tories be almost-unbackable favourites to win a seat they lost last time by nearly 3,000 votes? The answer, in one word: expenses.

David Chaytor, the current MP, learned last week he was to face three charges in relation to his parliamentary claims. He strongly denies claims of deliberate wrongdoing, but the allegations will inevitably cast a shadow over the next election.

Bury North is another seat lost to the Conservatives in 1997. Before that, it was held for many years by Alistair Burt, an Oxford-educated solicitor and former Bury Grammar head boy who has since returned to the Commons as a Tory MP in Bedfordshire. The Liberal Democrats have traditionally come a fairly distant third.

Labour have chosen their candidate well. Maryam Khan, daughter of former Manchester Lord Mayor Afzal Khan, represents a clean break from the past. She is bright, young, photogenic and down-to-earth. But she is not a miracle-worker.

David Nuttall, the Conservative candidate, left school at 18 before joining a firm of solicitors and getting a law degree in his spare time. He is active in his community and church and is a traditionalist making clear on his website that he would support capital punishment for murder, and reducing the time limit for abortions from 24 to 20 weeks.

The Lib Dems Richard Baum is an energetic young councillor and blogger who is tipped for big things in the future.

2005 result: Lab 19,130, Con 16,204, LD 6,514

Current odds: Con 1/6, Lab 7/2, LD 100/1

Manchester Withington - 2005: John Leech (LD), Majority: 667

My abiding memory of the 2005 election? A stunned John Leech taking to the stage at Manchester town hall, barely able to recite the victory speech he had barely bothered to write. It was an incredible win, overturning an 11,000-plus Labour majority and ending the Commons career of the respected Keith Bradley.

But the campaign was also a byword for bitterness. Labour activists still claim that the Lib Dems exaggerated fears, first expressed by doctors, over the future of services at the Christie hospital. The Lib Dems responded that they were simply campaigning to protect a world-famous resource.

What's beyond doubt is that Mr Leech has proved an extremely active MP, winning awards for campaigns on road safety and championing several high-profile local causes. In response Labour has rolled out one of its brightest young things, Lucy Powell, who was appointed director of the pro-European Britain in Europe campaign while still in her 20s. Withington, though, could yet prove a campaign too far.

And the Conservatives? They were a distant third in 2005. Yet until Mr Bradley was elected in 1987, Withington had been a Tory stronghold since before the Second World War. How times have changed for the Conservatives and how they hope they are about to change again.

2005: LD 15,872, Lab 15,205, Con 3,919

Current odds: LD 2/5, Lab 7/4, Con 80/1