Blair Alston’s late goal handed Partick Thistle a play-off lifeline but it is advantage Raith Rovers in the battle for promotion to the cinch Premiership.First-half strikes from Scott Brown and Lewis Vaughan at Firhill earned Ian Murray’s side a 2-1 lead after the first leg of the play-off semi-final.Thistle have now gone six games without a victory against the Kirkcaldy side, who finished 14 points clear of their opponents in second place in the Championship table.But substitute Alston’s 72nd-minute goal keeps the tie well and truly alive ahead of Friday’s second leg at Stark’s Park after Thistle finished strongly.While Thistle were beating Airdrie over two legs last week, Raith were able to get Liam Dick and Keith Watson back in their defence after injury while Dylan Corr, Dylan Easton and Josh Mullin were fit enough to be included on the bench.Watson hit an early chance wide before the Raith defence denied Aaron Muirhead and Kerr McInroy with blocks and visiting goalkeeper Kevin Dabrowski fumbled Aidan Fitzpatrick’s shot to safety.The opener came in the 22nd minute when Brown was first to Luke McBeth’s headed clearance following an Aidan Connolly cross. The Rovers captain volleyed the ball into the corner of the net from 12 yards.Chances kept coming at both ends. Vaughan fired just wide after bringing down the ball in the box, McInroy shot inches past a post after an excellent turn, and Kyle Turner curled high and wide after a clearance fell invitingly for the former Thistle midfielder.Vaughan doubled the lead five minutes before the break when he volleyed into the roof of the net after a Ross Matthews cross had skidded off the wet surface past two Thistle defenders.Dabrowski made an excellent stop from Scott Robinson’s first-time effort to protect the two-goal lead before the interval.Both sides were well aware the next goal would have a major bearing on the dynamics of the tie.Vaughan was inches wide with an ambitious effort just after the interval before Shaun Byrne pulled off an excellent defensive intervention to deny Ben Stanway at the other end.Dabrowski saved from Brian Graham from close range and Raith appeared to be successfully stifling their hosts, although they were fortunate that referee Chris Graham did not punish Brown for a lunge that got the ball but left McBeth hobbling.The Jags got their lifeline thanks to a simple long ball forward. Graham headed it on and Robinson somehow managed to nod it into the path of Alston despite falling over. The former St Johnstone midfielder’s shot bounced over the diving Dabrowski and into the net.The Raith goalkeeper pulled off excellent diving stops from Graham’s header and Alston’s first-time strike to keep his side in the lead at the halfway stage as the pair battle to play either St Johnstone or Ross County in the final.