While the Seasiders have now only a slim chance of surviving in the Nationwide Conference, United nudged into the top half of the table thanks to two fine goals by Robert Wolleaston who was unlucky not to end the game with a hat-trick.
Scarborough manager Neil Redfearn had a long inquest on the game behind closed doors as his side now has to rely on poor results from other teams in the Conference basement- although Altrincham's 18-point deduction for playing an eligible player has put them at the bottom.
David McNiven was unlucky not to give Scarborough a dream start after just two minutes but he fumbled his chance and United keeper Scott Howie was able to claim.
The home side created the better chances in the early stages thanks to Kevin Nicholson who put a speculative chance over the bar and McNiven put another effort on to the roof of the net before Tony Hackworth went close with a drive which David Bridges did well to clear out of the goalmouth.
But Cambridge gradually settled down and pulled off some promising replies with Jamie Guy creating a fine chance but there was no-one to force it into the net.
Redfearn, who had almost engineered a goal with Jimmy Beadle, put Scarborough ahead in the 36th minute from a great solo effort which he slammed into the back of the net.
Cambridge hit back and almost equalised when Jon Brady had a brilliant shot finger-tipped over the bar by Ian Dunbavin then just before the break Wolleaston scored his first after being set up by Ritchie Hanlon.
Courtney Pitt created a good chance to put United ahead only to see his attempt blocked by Rob Atkinson in the goalmouth, then Brady, Bridges and Guy each raised hopes before Wolleaston netted the winner in the 74th minute when Bridges slipped him the ball and he made no mistake.