Their dramatic last-gasp 33-30 win at Richmond secured a seventh successive league victory.
And a surprise home defeat for leaders Ealing Trailfinders against Bedford Blues saw Doncaster leapfrog the promotion favourites into pole position.
The top team will be promoted to the Gallagher Premiership – a system which will not return until 2025 due to changes voted through by the RFU Council last year.
Third-placed Ealing and fourth-placed Cornish Pirates both have two games in hand on Doncaster and trail the leaders by just three and four points respectively.
But an exciting end to the season could be on the cards with the Knights due to travel to Ealing on February 26.
Knights beat Ealing, whose financial resources far exceed their Championship rivals, at Castle Park earlier in the season. Steve Boden’s men prevailed 22-5 when the sides met in November.
Doncaster host Hartpury on Saturday (2.30pm). They have four games left to play.