Conor Thomas' late strike earned Cheltenham a 1-0 home win over Colchester and put them on the verge of automatic promotion from League Two.
The Robins' superior goal difference means they are all-but assured of a place in League One next season, while the victory saw them leapfrog Cambridge into first place.
One more point from their remaining three games will rubber-stamp promotion to the third tier.
The winning goal came in the 82nd minute when Thomas forced the ball over the line from close range after Liam Sercombe's corner on the right was flicked on by Charlie Raglan.
Raglan had earlier seen a header cleared off the line by Noah Chilvers after a long throw-in from Ben Tozer in the 29th minute.
Former Robins midfielder Harry Pell escaped with a yellow card after a lunging challenge on Sam Smith before half-time.
Cheltenham did most of the pressing in the second half, with Finn Azaz setting up Matty Blair for a shooting chance in the box, which was well-blocked by Miles Welch-Hayes.
Smith curled one wide after Sercombe's pass before Thomas broke the deadlock, while only some fine goalkeeping from Shamal George denied them a second as he kept out efforts from Alfie May and Callum Wright in the final seconds.