The Sulphurites are above Forest Green Rovers on goal difference having played a game fewer.
Stags fans will point to the part referee Paul Howard played, but they were already leading before Ollie Clarke and Stephen Quinn were sent off. It was not that they had outplayed Mansfield at that point, but in Luke Armstrong and Jack Diamond they have two real match-winners. Both made a big difference.
Armstrong scored an equaliser early in the first half and made Jack Muldoon's goal at the end of it. It was Diamond who was brought down by Clarke for a straight red card. Before play resumed, Quinn had been sent off for an off-the-ball incident which saw Josh Falkingham fall to the ground clutching his face.
In all Howard showed 10 cards.
Harrogate added one more goal in the final 15 minutes, the only surprise being that Armstrong was not involved.
Building on the foundations of a good debut Football League season, itself just a development of the team that won promotion from non-league, Armstrong's aerial prowess has taken Harrogate to another level.
Between the penalty areas there was little to choose between the sides.
Muldoon is used to shouldering the goalscoring burden for Harrogate, top-scorer in each of his three seasons, but now has others to help with the load. Danilo Orsi scored a Football League Trophy hat-trick against Mansfield in midweek but it shows how the competition is regarded that he was on the bench as both sides made wholesale changes.
Back in his place was Armstrong, signed from Salford City in the summer and with three goals to his name at kick-off. There was also a second debut for Jack Diamond, the winger on loan from Sunderland who was the only change from Harrogate's previous League Two game.
Mansfield were in front after only three minutes, Rhys Oates stretching onto a Stephen McLaughlin free-kick to the back post.
It took two minutes for Armstrong to respond, heading in the corner Diamond won, but Mansfield were much the more threatening side in the early stages.
Mark Oxley had to cut out the cross as McLaughlin once more aimed for Oates and George Lapsile shot over from outside the area.
As the half went on, though, Harrogate got to grips with the Stags and Diamond began to shine.
He produced a lovely an excellent tackle chasing Kellan Gordon back midway through the half and a lovely sweeping pass to George Thomson, but Armstrong's header hit a defender.
Lewis Page almost suffered a second insult on top of the one already added to his injury late in the half. He took an eye-watering cross right where he did not want to and as he was trying to run the pain off, was booked for a foul on George Maris a bit over 25 yards out. Fortunately for him, Oxley saved McLaughlin's free-kick and in first-half stoppage-time Armstrong touched a very good Pattison cross for Muldoon to finish.
The 49th minute summed up what was good about the visitors, Diamond repeating his lovely 18th-minute turn, carrying the ball to the edge of the area and winning a free-kick when his shot was blocked. Armstrong headed the ball in from it, but was offside.
It was another one of his runs which saw the game take a bizarre twist, beating debutant Rchard Nartey before being brought down by Clarke.
As soon as it became nine-versus-eleven it was just a question of how many more goals Harrogate could add.
Nathan Bishop did well to limit it to one, saving when Muldoon was played through, then doing even better to deny Armstrong with his feet.
Thomson rounded it off with a terrific header from a corner and George Maris pulled substitute Simon Power back to see the card count reach double figures.
Harrogate, though, are a team heading in the right direction.
Mansfield Town: Bishop; Gordon, Hewitt, Nartey, McLaughlin; Maris; O Clarke, Quinn; Lapslie (Johnson 68); Oates (Rawson 76), Hawkins (Bowery 82).
Unused substitutes: Shelvey, Burke, Sinclair, Stirk.
Harrogate Town: Oxley; Burrell, McArdle, Hall, Page; Thomson, Falkingham (Kerry 76), Pattison (Power 84), Diamond; Armstrong, Muldoon (Orsi 87).
Unused substitutes: Fallowfield, Martin, Cracknell.
Referee: P Howard (London).