Rangers failed to cash in on Celtic not being in action as they were beaten 3-2 at home by Dundee United.
Celtic's clash with Inverness Caledonian Thistle was called off on account of a waterlogged pitch and a win would have taken Rangers top of the SPL. They led on two occasions, but were pegged back before David Goodwillie popped up with a winner a minute from time.
Nikica Jelavic headed Rangers ahead on 19 minutes, thumping a free kick from El-Hadji Diouf into the corner. But they were back on level terms a minute from half-time when David Robertson raced onto Danny Swanson's pass and slotted home.
Rangers restored their lead in the second half when Steven Naismith pounced on a loose ball to score. The Gers failed to hold on to their lead as Johnny Russell before Goodwillie stunned Ibrox with a late winner.
Michael Higdon netted a brilliant second-half hat-trick as St Mirren battled back from a goal down to beat Hamilton 3-1. The win takes the Saints nine points clear of Hamilton at the bottom of the table.
Chris Humphrey inspired Motherwell to their second victory over Aberdeen since former manager Craig Brown's departure for Pittodrie as the Lanarkshire side opened up a four-point cushion in the race for a top-six place with a 3-1 win.
Humphrey blasted home inside 15 minutes and set up several more chances before Shaun Hutchinson looked to have made the points safe in the 87th minute.
Nikola Vujadinovic headed Aberdeen back into it in injury-time but Motherwell held on to move nine points above the Dons.
The clash between St Johnstone and Kilmarnock ended goalless.