Vale edged past Gillingham in the top-of-the-table clash at Priestfield.
All three goals came in the first 21 minutes, with Tom Pope and Lee Hughes putting the visitors 2-0 ahead before Danny Kedwell (21) pulled one back.
Exeter moved up to third with a 3-0 win at home to Southend, with John O'Flynn scoring either side of Scot Bennett's effort.
Rotherham are down to fourth after a surprise 2-0 home loss at the hands of Barnet, who scored through Jake Hyde and substitute Andrew Yiadom, while Cheltenham slip to fifth after being held 1-1 at home to York.
Shaun Harrad (67) put Cheltenham in front, but Jason Walker equalised six minutes from time.
Burton Albion are up to sixth courtesy of a 2-1 win over Torquay, who had taken the lead through Ryan Jarvis just before the interval. Calvin Zola (59) and Matthew Paterson (84) turned things around for the home side.
Bottom side Bristol Rovers enjoyed only their second away win of the season, hammering Fleetwood Town 3-0 thanks to goals from Danny Woodards, Eliot Richards and John-Joe O'Toole.
They are now just one point behind AFC Wimbledon, who were held 2-2 at home by Wycombe.
Paul McCallum scored twice after Jo Kuffour had given Wycombe an early lead, but the visitors claimed a point through substitute Matt McClure 18 minutes from time.
Plymouth moved above AFC Wimbledon thanks to a 2-1 home win over Morecambe, who could only manage an 80th-minute consolation from Ryan Williams after Conor Hourihane (10) and Paris Cowan-Hall (16) had put the Pilgrims in charge.
Elsewhere, Troy Brown and Daniel Lopez gave Aldershot a 2-0 win over Accrington Stanley, while Chesterfield eased past Northampton 3-0 thanks to a goal from James O'Shea and a Marc Richards double inside the first 25 minutes.
Peter Leven scored a 90th-minute penalty winner for Oxford at Bradford, who had seen Nahki Wells' early opener cancelled out by Sean Rigg (18).
And there was also a last-minute winner at Dagenham and Redbridge, where Medy Elito grabbed the winner for the home side in a 2-1 success over Rochdale. Andrew Tutte opened the scoring for the visitors on 72 minutes, but Abu Ogogo equalised just three minutes later.