Will McCombes be outfoxed by Colin for SSP?

But insiders say the head-to-head contest between Mr Fox and the party’s policy co-ordinator Alan McCombes could prove close.

There is little separating the two men ideologically, so the contest is largely a matter of style and personality. And one of the key issues has become whether the SSP should be led from inside the Scottish Parliament or outside.

For most other parties, there would be no question. The idea of a non-MSP leader would be unthinkable - although the SNP opted to be led from Westminster when it elected Alex Salmond.

But the SSP places great emphasis on its role as a grassroots party and it is reluctant to succumb to the attractions of what might be labelled "bourgeois" political status.

So the delegates at the SSP conference being held in Perth this weekend must decide whether they want the party led by an MSP able to command a high public profile or if it’s more important to underline their grassroots credentials by opting for a non-MSP.

Mr Fox believes being an MSP opens doors and wins access to places where the party could not otherwise reach.

"Electing a non-MSP as convener would make the job ten times more difficult," he says. "I don’t think Alan would get invited to many meetings because he wouldn’t be an elected representative."

But Mr McCombes claims many SSP members agree with him that a non-MSP would make a better leader for the party.

"The case for having a full-time convener outside the parliament, as against what would be a part-time media spokesman over and above parliamentary duties, has been powerfully received," he says.

The party’s six MSPs are split on who should get the top job - Tommy Sheridan and Rosemary Byrne are backing Mr Fox, while Rosie Kane, Carolyn Leckie and Frances Curran support Mr McCombes.

And among the wider membership, there is a geographical split, with Mr Fox able to rely on votes from the east and Mr McCombes stronger in the west.

Before being elected to the Scottish Parliament in 2003, Mr Fox spent five years as full-time organiser for the SSP in the Lothians.

Although he is based in Glasgow, Mr McCombes says he also has strong Edinburgh connections, having lived in the Capital for a while and with three daughters living in Newcraighall and going to school here.

The shadow of Tommy Sheridan will loom large over whoever wins on Sunday. The party has still not satisfactorily explained why the man who was so closely identified with the SSP’s success had to go.

And his absence will be noticed when it comes to the General Election. The SSP had a poor result in last year’s European poll, and the Westminster elections, without the advantage of proportional representation, are not fertile ground for the party.

But the Socialists are looking beyond the election, expected in May, to the G8 summit at Gleneagles in July, when they plan to make the most of the opportunity for marches and protests.

"It’s good timing for us," says one insider. "Mass protests are our kind of thing and it will give us a psychological boost after what might be a disappointing election."

Mr Sheridan is a hard act to follow and neither candidate for the succession makes any pretence of having the same charisma. Mr Fox has made clear he will not try to be a Tommy mark II. "I won’t start going to the sunbed," he jokes.

And Mr McCombes is also quick to admit the difficulty of following a star act.

"Following Tommy is like following Elvis in Las Vegas," he says. "But Colin and I would rather be compared with Scotland’s other political leaders. Compare us with Jim Wallace, Nicola Sturgeon, Jack McConnell, David McLetchie and Robin Harper and we can more than hold our own."