With Milton Keynes losing at Bradford on Monday and Swindon suffering the same fate at Oldham, Steve Cotterill’s men took full advantage with goals from Jay Emmanuel-Thomas, Joe Bryan and Matt Smith moving them four points clear at the top.
Emmanuel-Thomas broke some stern Vale resistance with a solo effort in the 34th minute, driving at the visiting defence before unleashing a fierce left-footed shot from just outside the box.
Bryan doubled the advantage just before the hour mark when his left-wing cross took a deflection to loop over goalkeeper Chris Neal and Matt Smith intercepted a poor back pass from Richard Duffy to make it 3-0 eight minutes later.
Mark Marshall fired a low drive past Frank Fielding 13 minutes from time for a Vale consolation before Emmanuel-Thomas hit a post for the hosts.
Both sides created opportunities in an entertaining scrap. Vale’s Chris Birchall headed badly over from the first good chance of the game after four minutes and Fielding had to make good first-half saves from Marshall and Michael O’Connor.
At the other end Carl Dickinson and Frederic Veseli produced heroic goal-line clearances to deny Aden Flint and Luke Freeman.