Continuing my look at the seats that will illustrate how well or how badly each party does at the election, here’s my pick for the Conservatives.

As with my lists for Labour and the Liberal Democrats, each of the 12 seats below represents a particular kind of contest, the result of which will serve as a measure of the Tories’ success – or failure.

1. Hampstead & Kilburn

Conservative target no. 1

The Tories’ top target was won in 2010 for Labour by Glenda Jackson, with a majority of just 42 votes. Jackson is standing down this year. Tulip Siddiq will be hoping to hold the seat for Labour, while Simon Marcus is the Tory candidate. It’s an intriguing contest whose result will offer clues about how well the Tories are doing in London, in whose favour the Lib Dem vote is collapsing, and how robustly Labour is seeing off challenges from the Tories.

2. Derby North

Conservative target no. 7

Labour’s Chris Williamson has a majority of only 613 in Derby North. If Ukip-inclined supporters vote tactically, and if the left-wing vote is split, the Conservatives may end up winning the seat. It’s the sort of scenario the Tories will be relying on to chip away at Labour’s overall tally of constituencies, and it’s places like these and Southampton Itchen (which is on my list of Labour’s decisive dozen) that could deliver David Cameron a second term in power.

3. Wells

Conservative target no. 10

The sort of Liberal Democrat seat the Tories ought to be able to take fairly simply. They need only a 0.7% swing to overturn Tessa Munt’s majority of 800. Watch to see how easily Tory candidate James Heappey wins the seat. If he manages a majority of around 3,000, that will be a very good result indeed. Anything around 1,000 could mean the Tories will struggle in their quest to take up to eight Lib Dem seats across south-west England.

4. Berwick-upon-Tweed

Conservative target no. 43

Sir Alan Beith is standing down from the seat he has held for the Liberal Democrats continuously since 1973. His majority in 2010 was only 2,690. The Conservatives need a swing of 3.5% for a victory, and they’ll be confident of success. It’s certainly the kind of seat the Tories need to take to ensure they remain the largest party in the House of Commons.

5. Carshalton & Wallington

Possible Conservative target

Tom Brake has held Carshalton & Wallington for the Liberal Democrats since 1997. This will be his sixth election contesting the seat. The Tories’ Matthew Maxwell Scott needs a 5.8% swing to win: a tough challenge, but both he and his local party think it can be done. If Scott is victorious, it will mean the Tories could end up knocking out at least a dozen Lib Dems. This would be a big help in offsetting potential losses elsewhere to Labour.

6. Thurrock

Labour target no. 2 (and Ukip target)

This is a fascinating contest that has become a three-way battle between sitting Tory MP Jackie Doyle-Price, Labour’s Polly Billington and Ukip’s Tim Aker. Doyle-Price has a majority of only 92. The seat ought to be an easy Labour gain, but Ukip think they’re in with a chance of an upset, and Doyle-Price is a sharp campaigner. Much will depend on tactical voting, especially from people who are anti-Ukip and who’ll need to decide whether Doyle-Price or Billington is best placed to defeat Aker.

7. Plymouth Sutton & Devonport

Labour target no. 20

One of the few Tory seats in southern England that Labour has a good chance of taking. Oliver Colville would lose on a swing of just 1.3%. This kind of seat represents the Tories’ first line of defence. They could feasibly lose constituencies like Plymouth Sutton & Devonport and still end up the largest party in parliament, so long as the defeats are limited to seats in Labour’s top 20, and the Tories can compensate with gains from the Liberal Democrats.

8. Northampton North

Labour target no. 39

A textbook bellwether seat. Since its creation in 1974 its voters have always elected an MP from the party that has gone on to win the general election. Labour needs a swing of 2.4% to defeat the sitting MP Michael Ellis. If the Tories hang on to places like this, we’ll be heading for an awfully close result where a only tiny handful of seats may separate the Conservatives from Labour.

9. Loughborough

Labour target no. 51

A critical seat for both the Tories and Labour. If Labour wins here, they’ll have achieved the sort of swing (3.5%) needed to become safely the largest party in the new parliament. This is also the seat of education secretary Nicky Morgan, so there’s the added attraction of defeating a high-profile member of the cabinet. The Tories will do all they can to save Morgan, however, and constituents can expect a string of visits from senior Conservative ministers between now and polling day.

10. Ilford North

Labour target no. 83

If this falls to Labour, the Tories really will be in trouble. It could also be evidence of the party doing particularly badly in London, where they stand to lose potentially up to nine seats to Labour. Wes Streeting needs a 5.8% swing to take the seat from Lee Scott.

11. Oxford West & Abingdon

Lib Dem target no. 4

Tory MP Nicola Blackwood has a majority of only 176 in this seat, and though I don’t think she’s in any danger of losing the seat, it’ll be worth watching to see how she does this time. If she manages a comfortable win, it’ll be evidence of a fracturing of the anti-Conservative vote – something that might help the Tories elsewhere in the country. If it’s another narrow result, however, it’ll be clear the Tories aren’t doing as well as they hoped in former Lib Dem strongholds.

12. Dumfriesshire, Clydesdale & Tweeddale

This is the Tories’ only seat in Scotland. It is notionally a Labour target, with the party needing a swing of 4.6% to take the constituency. But the SNP will fancy their chances here, despite needing a 13.6% swing for victory. A lot will depend on the behaviour of former Lib Dem and Labour voters. If the anti-Tory vote ends up being split three ways, David Mundell could well hold his seat.