A clock on Ken Livingstone's campaign website counts down remorsely the days, hours, minutes and seconds to polling day in London, when about 5.8 million voters decide which candidate will be mayor and run the capital for the next four years.

But Livingstone, engaged in a longstanding campaign to use the rematch with London's Tory mayor, Boris Johnson, to wrest back the mayoralty, is struggling to make his strategy count as the latter outperforms his own party and his Labour rival.

Separate elections are being held on 3 May next year for London mayor and the 25-strong assembly. The next mayor to run a capital with a population of 7.8 million faces a number of challenges thrown up by economic and transport problems, as well as the summer riots and the dire shortage of affordable housing in a city where benefit changes will hit the poor particularly hard. The mayor will also get the prestige role of presiding over the 2012 Olympics.

Voting tendencies for the assembly polls tend to align more closely with national party share, but all eyes are on the razzmatazz of the mayoral contest. It is widely seen as a two-horse race involving a pair of larger than life characters with mayoral records to defend, known on first-name terms by the entire country, each willing to speak against the party line when needs must, with a mutual tendency to outpoll their parties.

A YouGov survey in June revealed that one in five people who would vote Labour in a general election said they planned to vote for Johnson next May. Those factors make Livingstone's line particularly difficult and there have been signs over the last year that his team is vacillating on the line of attack.

In September 2010 Livingstone used his victory speech on being selected Labour candidate over his rival, Oona King, to make clear he would fight on an anti-government ticket. Selected the day before Ed Miliband was declared party leader, Livingstone cast the mayoral race as a referendum on the coalition, by urging Londoners in a Labour-leaning city to "send a message" to David Cameron and George Osborne over spending cuts by "getting out Boris".

But this year Livingstone has concentrated on Johnson's record in office, casting the race as a "direct choice" between a candidate whose mission as mayor would be to protect Londoners from rising living costs, and an "out of touch" Conservative.

Tapping into the anger of those who think the banks and the City got off lightly following the 2008 crash, Livingstone has seized on Johnson's defence of the financial sector and his call for the 50p top rate of tax to be abolished, and set himself up as the man for the "99%" against "privileged" Johnson batting for the 1%.

But polling by ComRes in November indicated that attempts to portray the popular Tory as a privileged, out-of-touch toff were not working. Johnson had an eight-point lead over Livingstone (54% to 46%), when other candidates were stripped out, gaining a bigger winning margin than in the 2008 election, when he finished six percentage points ahead of Livingstone in the first-preference vote under the supplementary vote system.

The survey also showed the incumbent mayor to be the candidate most trusted on crime, the economy and policing, indicating he had earned credibility in running the city. His weakness was transport; on this Livingstone led as the most trusted, suggesting early gains following the promise to cut fares by 7% compared with Johnson's 5.6% fare rise.

Peter Kellner, president of YouGov, said these most recent findings underlined the need for Livingstone to "depersonalise" his campaign against Johnson and focus exclusively on policy.

Kellner said: "At the moment the Conservatives are doing a good job nationally for passing the blame for the economic failure on Labour, and Boris is doing a good job to distance himself from the more difficult things [in] the government.

"If the campaign is perceived to be personal between Ken and Boris then Boris will win. Ken had the personality votes in 2000 and 2004, but Boris has them now.

"If the campaign is to be about the future of London, transport, housing and the state of the economy, then I think Ken can win. But that depends on how the candidates behave, how the media behave and how voters perceive it. If Livingstone can get half that vote back he could win because London is, relative to the rest of the country, a Labour city."

But documents seen by the London Evening Standard last week suggest a return to the earlier line of attack. This follows media reports that Cameron told a private meeting of Tory MPs that winning a second-term Conservative mayoralty was his "number one priority" for 2012, aware his policies and the economic slowdown would be blamed if Johnson lost. The Livingstone idea is to "Tory-ise" the Boris brand, and cast him as a "true blue" Conservative whose re-election would be a boon to Cameron.

A document written by Simon Fletcher, Livingstone's former chief of staff and campaign manager, states: "Our campaign team need to use every opportunity to point out how being tied to the Tories is highly toxic for Boris Johnson with many voters – and it is Cameron himself who is binding Johnson to his mast."

Tony Travers, director of the Greater London group at the London School of Economics, says a contest driven by popularity would make the result a close-run thing. But he says the notion of the mayoral race as a political test of the parties nationally, in the midterm of the Westminster parliament, risks causing more pain to Ed Miliband than Cameron.

Lord Mandelson recently became the most senior Labour figure to express concerns at Miliband's leadership performance and indicated that the Labour leader needed to show progress in 2012.

"There is more pressure for Miliband than David Cameron, in the sense that if Boris loses it will be seen as the midterm blues," says Travers. "If Ken doesn't win midterm in a coalition government, it will be worse for Miliband. The only real problem for Cameron would be that if Boris loses, he will try and get back into Westminster."

Other candidates also limbering up include Jenny Jones, the Green party candidate, and for the Liberal Democrats Brian Paddick, the former Met deputy assistant commissioner, who came third in the 2008 race. They are widely expected to use the race to raise their respective parties' profile for the more anonymous assembly elections.

Both leading candidates have their core teams firmly in place, with Lynton Crosby, the Australian political strategist who led Johnson's successful campaign in 2008, back in harness.

Crosby brought out the Conservative vote in the outer suburbs last time – the so-called "doughnut strategy" reflecting the outer ring of the capital. He says Johnson has disproved those who said he was not up to the job or would prove to be a "hard-right Tory Thatcherite" in power. "People in London want a champion and I think Boris has shown himself to be a champion."

Crosby says Johnson has been in every borough across inner and outer London more often in four years than Ken had done in eight, a fact that had helped him connect to people whose votes weighed equally at the election.

Livingstone, however, is "quite confident" he can turn things around. His team have circled 3 January – the date Johnson's fare rises kick in – for a mass leafleting exercise contrasting the mayor's fare rises with Livingstone's Fare Deal pledge, which, he claims, will save Londoners £1,000 on average over four years.

He insists this cut can be funded using the "operating surplus" budget sitting in TfL's coffers – a claim flatly rejected by the body chaired by Johnson, which says every penny is accounted for with regard to improving London's transport system.

Livingstone believes the polls will change once people have to pay the new fares. "If you actually look at the polling and you plough through the poll, Boris is the only Tory in Britain who still has a positive popularity rating, but that's based on the fact that it's on the soft issues."

He adds: "Boris has refused to debate with me for three and a half years … Once you hit the elections, where there's a detailed focus and people start to think 'what does this mean for me?', he can't get away with that."

On fares, Johnson retorts: "I think Londoners have heard twice before from that particular candidate promises to hold fares down, which were then flagrantly broken. So I take those promises with a pinch of salt, and if they were to be fulfilled, taking £1bn off TfL's investment programme I think would be wrong for the city."

Asked whether he feels cheered by how the polls are heading before his own campaign has even started, Johnson wards off complacency by muttering that "polls come and polls go".

He lists commitments he has delivered for the capital as he sits on a new Routemaster bus – a cleaner, greener, 21st-century version of the hop-on hop-off vehicle. Eight such buses will be on London's roads by late February.

"I'm going to fight very hard," says Johnson. "I think we've got a great record and I think if you look back at the things I said I would do and the things we've done, I think it's very considerable."