Paul Mullin's 30th goal of the season earned leaders Cambridge a controversial 1-1 draw in their top of the table Sky Bet League Two clash at Tranmere.
Mullin, scorer of 12 goals in 56 appearances for Rovers, saw a disputed 60th-minute penalty for a foul on Luke Hannant saved by 39-year-old Joe Murphy.
But the former Prenton Park marksman netted the rebound to keep Mark Bonner's side unbeaten in five and two points clear of second-placed Cheltenham.
Tranmere, vastly improved from their 4-0 Good Friday drubbing at Cheltenham, move into an automatic promotion place.
However, Keith Hill's side will feel they should have taken all three points instead of a fourth draw in six games.
Former Cambridge midfielder Paul Lewis fired the home side into a 10th-minute lead with his seventh goal of the season after latching onto a fine pass from Danny Lloyd.
Despite losing veteran midfielder Jay Spearing to injury, Rovers almost doubled their lead in the first half. Liam Feeney curled a free-kick onto the crossbar while Danny Lloyd carelessly shot wide from a good position 10 minutes from the break.