I very rarely make predictions on this blog, but having thought about this subject so much recently I'm going to stick my neck out and make two tentative forecasts for next May : 1) the two radical left parties will between them take either zero seats or one seat, and 2) if they take one seat, it will be Solidarity that pulls it off, not RISE. If RISE are going to make even the most modest of breakthroughs, they've got less than six months to go from virtually zero support to at least 5% in one of the eight electoral regions. That's not going to happen without a bandwagon effect, and you can't generate one of those out of thin air. When the SSP managed it in 1999 and 2003, it was largely founded upon Tommy Sheridan's fame and charisma. Colin Fox is not a Sheridan, and neither is anybody else in RISE. They're probably quite glad about that in some ways, but it does mean there is a limit upon their realistic electoral ambitions.
Solidarity are more fortunate, because they do have a Sheridan, and his name is Tommy Sheridan. It's interesting looking back to the last time that he stood in Glasgow in 2007 - the fading of his magic was such a landmark moment that we tend to overlook the fact that he didn't miss out on holding his seat by all that much. Solidarity got 4.1% of the vote, which meant they were just 1.1% away from denying Patrick Harvie of the Greens the final seat (and how that might have changed history if they had done). And do you want to guess what percentage of the vote the SSP got in Glasgow that year? That's right - 1.2%. It's all very well for the small parties to complain about being branded as "vote-splitters", but in reality it's themselves that are the biggest victims of that problem. The true threat to a radical left party claiming a seat next year may well be RISE itself.
Sheridan was in prison by 2011, so he temporarily vacated the field in favour of his old friend George Galloway and Respect - a bizarre decision, given Galloway's hostility to the cause that has defined Sheridan's career ever since that election. But it's plausible to suppose that Respect basically inherited the Solidarity vote in Glasgow, and there wasn't all that much further slippage - they got 3.3%, while the SSP only slipped to 0.7%. So there clearly is a lingering radical left vote in the city, and it might be just about sufficient to sneak one seat once Sheridan's stardust is reintroduced into the equation (especially now that he's been redeemed in some people's eyes by his passionate campaigning during and after the referendum). But even if that's the case, everything will hinge on whether Solidarity can keep RISE down to a derisory vote. I think the odds are against them, but on past form it's certainly possible.
It wouldn't surprise me if RISE outpoll Solidarity in the other seven regions (albeit without coming close to winning a seat), but it seems almost inconceivable that Sheridan will be eclipsed by his former colleagues on his own home patch.