Captain Andy Crosby hit the second, before supersub Cleveland Taylor came off the bench to strike a late double.
Laws said: "I thought that Cambridge were a shade unlucky to fall behind, but as soon as we got a grip, there was no way back.
"There's no sympathy down at the bottom, it was up to us to be as emphatic as possible and after the second goal we looked much more comfortable.
"These are tense games, whether you are top or bottom. We got four great goals and Taylor's great forte is to come off the bench and use his speed.
"We have great belief going into the last three games, our destiny is in our hands, I've said to the players let's go and get the championship, but there will be some twists and turns."
With Rushden beating Boston, Cambridge are left nine points from saftey with just three games to play.
It means anything other than three straight wins will condemn them to Conference football next season, as would Rushden picking up a point.
Cambridge boss Steve Thompson admitted: "This is the hardest job in football, but we are up for our next three games and we will do our best.
"If players are committed to the club I will give them a chance, but when you are bottom of the league things tend to go against you.
"The players have given their all, but we now have a mountain to climb and confidence is only built by winning.
"The problem is nobody knows what's happening off the field. Our fans and there were 400 of them here today have been terrific and they deserve better."