Labour's Sarah Boyack is hoping to fend off a challenge from the Liberal Democrats, who need a swing of just under five per cent to take her Edinburgh Central seat - on paper, their best chance of a gain anywhere in the country.
Lib Dem sources claim victory is looking "very probable". Candidate Siobhan Mathers says people are fed up with Labour and want a change. She admits most of the discontent is focused on Tony Blair and Labour at Westminster over issues like Iraq and ID cards.
"They are a bit fed up with Scottish Labour but people don't hate Jack McConnell the way they hate Tony Blair," she says.
Ms Boyack has strong green credentials, has spoken out against Trident and has a good reputation as a constituency MSP. But if the tide is running against Labour, can she hold on?
Ms Mathers says: "She is out of step with her party. Her environmental credentials will win her support in some places, but most people will vote on what the party stands for rather than an individual track record."
Ms Mathers became the Lib Dems' candidate in November after the previous candidate was edged out for, as a senior party source described it, "not showing the commitment required in a target seat".
She expects to do well among students and among Green voters since the Greens are only standing on the list.
Ms Boyack says she is running a positive campaign on her track record as MSP, supporting local campaigns for sports facilities, campaigning to save bus routes and responding to problems of anti-social behaviour.
She claims her canvass returns show the Lib Dems flatlining.
"There are a lot of undecideds out there," she says. "People are thinking about the SNP but a lot of people have worries about local income tax."
Ms Boyack acknowledges some discontent with Labour. "Obviously some people are unhappy after eight years in the Scottish Parliament and ten years in UK.
"But people can see the real difference new schools like St Thomas's have made."
SNP candidate Shirley-Anne Somerville says a high population turnover in the constituency means the Lib Dems cannot rely on their second place in the last Holyrood election as a base to build on.
She says: "The Lib Dems are looking back to 2003, but the number of people who have moved in to the constituency since then is vast and we are picking up a lot of votes."
Like Ms Mathers, Tory candidate Fiona Houston was a late entry to the race after former hereditary peer Jamie Sempill stepped down.
• The candidates are: Sarah Boyack (Lab), Fiona Houston (Con), Siobhan Mathers (Lib Dem), Shirley-Anne Somerville (SNP).