Third placed Motherwell moved up to 16 points in the Scottish Premiership after beating St Mirren at Fir Park on Saturday.
Goals by James Scott and Chris Long in either half won the day for the Steelmen.
St Mirren created a half chance after six minutes when Ilkay Durmus's cross from the left was nicked well wide of the far post by Jon Obika.
The next goal attempt came at the other end three minutes later when James Scott cut in from the flank and sent a low left footer off target.
And the hosts came close again when Liam Polworth's right footed drive forced Saints keeper Vaclav Hladky into a smart diving save low to his right after a pass inside by Sherwin Seedorf.
Then Seedorf himself glided in from the left and brought a save out of Hladky.
On 15 minutes, Motherwell centre back Declan Gallagher showed his attacking qualities by rampaging down the right wing and crossing for Devante Cole whose shot was blocked by Saints defender Calum Waters.
Polworth dragged an 18th minute shot wide from a Scott pass following a quick Steelmen breakaway.
Kyle Magennis's deflected shot from outside the box on 22 minutes was comfortably fielded by home custodian Mark Gillespie.
St Mirren's Sam Foley sent a rasping left footer just over from 20 yards before a swift Motherwell breakaway culminated in Campbell and Scott setting up Polworth whose shot was blocked by Hladky.
Motherwell went close again on 36 minutes when more fine play by Polworth sent Cole clean through but his effort was blocked by the advancing Hladky.
The Steelmen went ahead in fantastic style on 38 minutes when fine interplay between Polworth and Scott culminated in Scott unleashing a stunning 20-yarder into the top right corner giving Hladky no chance.
St Mirren made a storming start to the second half, with Durmus's long range drive tipped over by Gillespie at the expense of a corner. When it was swung over, there was a stramash in the box which led to Paul McGinn having two efforts blocked.
Motherwell replied with a Seedorf run and shot blocked by Hladky.
Sloppiness in midfield from the Steelmen then led to Saints' Foley rampaging through but his parting shot was straight at Gillespie.
Fine play between 'Well youngsters Maguire and Campbell sent Seedorf through on 68 minutes but his goal attempt went out for a throw-in.
A fine move by the hosts saw Jermaine Hylton and Campbell set up Polworth whose shot was brilliantly turned round the post by Hladky.
Home skipper Hartley came to his side's rescue on 71 minutes when he blocked Magennis's close range shot after Durmus's cross from the right.
Hartley then made a brilliant last ditch tackle on Obika as he ran through on goal.
Ryan Flynn missed a great chance for St Mirren on 81 minutes when he ballooned the ball well over after build-up on the left by Magennis.
Motherwell wrapped up the points on 85 minutes when a misplaced Saints pass was pounced on by substitute Chris Long who cut inside and smashed the ball home impressively.
Sean McLoughlin sliced an effort wide late on for the Paisley side.
Motherwell: Gillespie, Hartley, Gallagher, Tait, Grimshaw, Maguire, Campbell, Polworth, Cole (Ilic 79), Scott (Hylton 55), Seedorf (Long 68).
Referee: John Beaton