Yet the visitors, who lost for the first time in six games, dominated the first half and should have been out of sight by the time substitute Mayor settled matters with a 77th-minute screamer.
James Brown poked a weak shot at Thorsten Stuckmann before the goalkeeper saved from Antony Sweeney and the loose ball evaded Andy Monkhouse.
Then Luke James, Hartlepool's teenage talent again watched by a pack of scouts, tore past defender Jamie McAllister and curled a left-foot shot inches wide of the far post with Stuckmann beaten.
Preston's first shot on target came with the goal. Mayor ran at the defence after cutting in from the left and unleashed an unstoppable shot past Scott Flinders.
Hartlepool wasted four chances to level in the 90th minute. Substitute Colin Nish was denied by Stuckmann and Nicky Hunt blocked the follow up on the line. Monkhouse headed against the crossbar and then nodded the rebound wide.
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