Yemi Odubade grabbed a second-half double as Stevenage came from behind to see off Mansfield and replace Oxford at the top of the Blue Square Premier.
Jon Shaw smashed a shot into the far corner to give Stags a half-time lead.
But Odubade, who also missed a late penalty, fired Borough level from 15 yards after the break and his low drive from the edge of the box made it 2-1.
Substitute Andrew Drury's strike sealed the win and Mansfield's misery was complete when Luke Jones was sent off.
Jones received his marching orders for a professional foul on Odubade in the box with just six minutes left but the former Oxford man saw his resulting spot-kick saved by keeper Alan Marriott.
But, by then, the visitors' chances of salvaging something against their promotion rivals had long since gone.
At half-time the Stags looked well set having had the better of the play. They twice hit the woodwork in a fiery encounter, Shaw smashing a superb long-range shot against the bar and Gary Mills also hitting the foot of the post with a free-kick.
But Stevenage improved after the interval and, after Odubade's two goals in 15 minutes, Drury sealed the win within two minutes of coming on when he collected Jon Ashton's pass and shot into the top corner.
The victory sends Stevenage three points clear of Oxford, who lost 2-1 at Luton.
Mansfield Town manager David Holdsworth told BBC Radio Nottingham:
"We played against a good side who are up there and we had them on the rack.
"I thought we governed the game for long periods.
"They certainly showed the right spirit and the right endeavour, but it's just that little bit of luck at the moment, we seem to be getting balls spinning away, hitting posts and crossbars."
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