From eternally Tory Eastbourne to the Labour heartlands of West Yorkshire, the Liberal Democrats are convinced that they can take seats off both main parties at the forthcoming general election and end up holding the balance of power in a hung parliament. Could it really happen?

Annemarie Field smiled, her pale blue eyes sparkling in the sunshine. “I always used to say that if you put a blue rosette on a cornflakes packet it would win a general election in Eastbourne. This town is Conservative.” She should know, having worked for the town’s two local papers since 1985. But this year might be different.

Eastbourne is one of the top target seats for the Liberal Democrats, who are determined to overturn a Tory majority of 1,124. Field described the party’s campaigners as an army of “yellow ants” marching through the streets. With two months to go, they are delivering 45,000 leaflets and 25,000 targeted letters every fortnight. Their candidate, Stephen Lloyd, will knock on 2,000 more doors before 6 May.

“We don’t have multimillion-pound donations from Lord Ashcroft or the unions,” said Danny Alexander, the MP who chairs the group in charge of the party’s manifesto. But the Lib Dems appear to have something else: an unprecedented ability to organise locally.

That is what they are doing against the Tories in the south – and against Labour, largely in the north. It is a geographical spread which brings accusations that the party changes its message to suit its audience.

In this seaside town, the Lib Dems’ focus has been car parking – and, in the wake of the MPs’ expenses scandal, on the sitting Tory MP’s second home.

“The Lib Dems are desperate for Eastbourne,” said Field, walking into the newspapers’ main office. “If I was a gambling person I wouldn’t know who to put my money on,” she said to a male colleague. He swung his chair round to face her and nodded. “In fact, I might put my money on Stephen Lloyd,” he said. “Me too,” boomed another, raising his arm.

It is not only in Eastbourne where the Liberal Democrats are increasingly optimistic. At their party’s spring conference in Birmingham this weekend, the same conversations could be heard in the hallways, the restaurants and the bars. There was talk of whether the party could gain from public fury about expenses; debate about how the words “hung parliament” had thrown the party into the news like never before; chatter about whether Nick Clegg could exploit his role as equal player in the three televised leaders’ debates.

By yesterday many were daring to consider the question: could the 2010 general election be a turning point? They were boosted by the news that Edward McMillan-Scott, a former Tory MEP who once headed the party’s grouping in Brussels, had joined the party.

Then there was the rallying call from their leader. “On Monday morning I want you to get out there and go for broke in what will be the biggest fight of our political lives,” he told delegates, who rose to their feet and roared in appreciation. It all sounded good, but then again hadn’t they heard it all before? Wasn’t it much more likely that the activists dressed in yellow would wake up on the morning of 7 May disappointed again?

Some disagreed. “I think this election is starting to look different,” said Olly Grender, a former party director of communications who worked with Paddy Ashdown. “What is uniquely interesting is the strength of feeling that it is time for a change, and the same strength of opinion that David Cameron is not the embodiment of that change. That creates an opportunity for the Liberal Democrats.”

Grender said the televised debates were vital. The fact that broadcasters, and in particular the BBC, were taking the party seriously would create a “ripple effect”. Then there was the “hung parliament scenario”, which Grender called a “double-edged sword”. It made the party relevant but also raised fears among voters of its economic dangers.

“I headed the media in 1992 and anyone involved in that campaign came out deeply scarred,” said Grender, as he recalled the “absolute certainty” with which pollsters predicted a hung parliament in the exit polls and the “absolute nonsense” that proved to be the cold light of day.

Grender said it was “critical” that Clegg was not drawn on the issue. On Friday he wasn’t. On stage, he referred to “you know what”, baiting journalists looking for any sign that he was ready to make a pact. Clegg lifted up his red tie, then smiled and pulled open his jacket to reveal a blue lining.

Today he will tell delegates in his conference speech that it is for the public to decide. “I am not a kingmaker. The 45 million voters of Britain are the kingmakers. They give the politicians their marching orders, not the other way around. It’s called democracy,” he will say.

Clegg says his party is interested in promoting its four main areas of policy focus: tax, education, cleaner politics and the financial crisis. Nevertheless, fears emerged among left-of-centre delegates at the weekend that he would get too close to Cameron .

Yesterday evening MPs and others gathered for a fringe meeting to formally launch the Social Liberal Forum – a pressure group committed to “reinventing the left” in Britain. Some admitted they were uneasy about the notion of a Tory-Lib Dem pact.

Clegg had aimed to reassure delegates by clarifying comments that appeared to support the former prime minister, Margaret Thatcher. “I violently opposed and was hostile to pretty well everything she did,” he said.

But Grender argued most delegates would not put themselves on the left-right political spectrum. “There is a strength of philosophy and it is liberalism.”

Many people spoke at conference about what was happening outside, on the streets of Birmingham, through Yorkshire and into Newcastle, across Cambridge, London and into the south-west. Tim Farron, who is defending a majority of only 267 in Cumbria, told delegates that the Lib Dems had to deliver 10 times more leaflets that their rivals just to be heard. In a rousing speech, the MP compared the campaign to a football match in its final five minutes.

John Curtice, professor of politics at the University of Strathclyde, said he had seen activists in action in his own constituency and “boy, are they fighting for it”. But he also introduced a dose of realism, saying that the national polls suggested the party was “indestructible yet uninflatable”. That said, the key to the general election could be the Lib Dem-Tory marginals, he said. The results there could determine whether or not Cameron won his much-yearned-for majority.

In Eastbourne, seagulls flocked above the union flag flapping in the wind over the station, beside neat, landscaped gardens which run parallel to the beach and above rows of well-kept, sizeable homes. At 100 Seaside Road last week, the windows were filled with yellow and orange posters. Four volunteers sat inside the front room rhythmically picking up leaflets and stuffing them into envelopes.

This war room has been active for years, not months, funded by Lloyd and a large number of relatively small donations. The candidate’s message is persistently local: his three top issues are a campaign against a parking scheme, a fight to save a local college and policing.

As one of the writers at the Eastbourne Herald claimed: “You can’t win in Eastbourne with Lib Dem policies.” And Lloyd’s team were having “field day” attacking the local Tory MP, he added, largely because it had emerged that Nigel Waterson’s children went to school near a home he owns miles away in Beckenham, Kent.

“I live locally, I shop locally, I know the issues that people experience every day because I experience them too,” said Lloyd, repeating the mantra he has used to the people of Eastbourne.

The other message repeated again and again was that only the Lib Dems could beat the Tories in Eastbourne. Lloyd, whose own roots are in the Labour party, said he was grateful for the votes Labour supporters might bring.

The Tory response is to stress the other side of the equation. “The question that matters in this is election is whether people want five more years of Gordon Brown or David Cameron and the Liberal Democrats do not feature in that,” said Waterson. He criticised Lloyd’s campaign as “particularly nasty and personal” and warned it could backfire.

But if the question for the Lib Dems in affluent towns in the south-west is how to persuade Labour supporters to back their assault on a Tory incumbent, how can it challenge Labour in some of the most deprived wards in the country? Does it cynically change its message to boost its chance of election?

Bradford East is another seat the Lib Dems are desperate to secure – this time by seizing it from the Labour MP, Terry Rooney. In 2005 it wasn’t a target. The candidate, David Ward, remembers the “battle bus” flying straight past his office on its way to Leeds North West. “But this time it will stop,” he said. “The party is relentless with target seats.”

Ward’s constituency was added to the list two years ago and since then central office has demanded monthly updates about the number of leaflets and letters dispatched and doorsteps trodden. Clegg has already visited a number of times.

Ward drove his car around the constituency to demonstrate its diversity. He passed through the attractive cottages at the northern tip, before turning in to one of the most deprived estates in the country. Some of the houses lay deserted with huge metal plates hauled up over windows and doors. At others the gates had fallen off their hinges.

The estates gave way to Bradford Moor, where shops such as Sana Fabrics, Ahmed Foods, Nangla Furniture and Akbar’s lined the streets. In Bradford East half the children were on free school meals, there were five big working-class estates and in the poorest ward a child was five more times likely to die than in Ilkley, an affluent spa town outside the city, said Jeanette Sunderland, the leader of the Lib Dems on the local council and Ward’s campaign manager.

Sitting back into her chair in the campaign headquarters, she flung her hand up towards a map of the sausage-shaped constituency, colour-coded by deprivation. “That means poverty,” she said, sweeping her hand over the lower half of the map, which was red. “And no one lives up there,” she said, pointing to the smaller area of blue.

Behind Sunderland stood a flip chart on which were written four key policies for the Lib Dems. “We take the complex national messages and we explain why they matter to you in Bradford East,” she said. “The £10,000 personal income tax allowance will benefit everyone, while the mansion tax on homes worth more than £2m will hit no one. There are no millionaires in this constituency. There isn’t a house worth £1m, never mind £2m. And the pupil premium to target the most deprived school students will bring in £12m.”

Here too, leaflets are being printed in the thousands. And it is an example of another way that the Lib Dems target areas – starting with a council seat, then another, until they have a ward, then two, then more. Finally, as is now the case in Bradford East, they throw all their energy into securing an MP.

Here too there is leaflet after leaflet reminding voters that there is one party that can’t win: this time, it’s the Tories.

Both Sunderland and Ward rejected the claim that the Lib Dems changed their message to suit the town. Sunderland said it was about talking about the parts of the message that were relevant . “In Little Horton ward in Bradford there is no point talking about tax – most are on benefits,” she said. Electoral reform was a non-issue in Bradford, especially for families where the decision was whether to eat or warm their houses.

Ward claimed disillusionment was rife in Bradford East. To prove his point promised that the first person he asked would not know the name of their local MP. He was right. “I haven’t got a clue,” she said in a strong local accent, laughing. Mubarak Khan, a 42-year-old taxi driver, said he had always backed Labour but now wouldn’t bother voting at all. “They promise and don’t deliver – on education, health, transport, even policing. I won’t be voting.”