Rangers are four points above Celtic at the top of the SPL after Saturday's 5-0 win at Motherwell, while Hearts drew 2-2 at Kilmarnock.
Kyle Lafferty, Steven Davis and Nikica Jelavic all grabbed a goal apiece for the Gers at Fir Park and Steven Naismith claimed a late brace as the champions stretched their lead at the summit to four points.
The onus is now on Celtic to respond to the pressure and put points on the board against Dundee United on Sunday and then make the most of their game in hand at Inverness.
In the day's other top-half game, Hearts edged closer to a Europa League place despite Kieran Agard's first senior goal snatching a 2-2 draw for their hosts Kilmarnock.
Hearts had come back from James Fowler's brilliant opener 10 minutes into the second half when Rudi Skacel and Ryan Stevenson netted.
