Dundee United were forced to fight back from behind to sink rock-bottom St Mirren 2-1 and move to the top of the Scottish Championship.The visitors grabbed a shock 27th-minute lead through John Sutton, but their advantage was immediately ruled out by Scott Fraser's equaliser.The hosts' pressure paid off in first-half injury time when Simon Murray headed home a Fraser set-piece to put them in front.Murray, Sean Dillon and Coll Donaldson all had chances to increase the home side's lead as they dominated the second period.