Mulroy shares the 54-hole lead with Chris Tidland (68) at 10-under-par 206. Mulroy will go for his first Nationwide Tour win on Sunday, while Tidland will got for his second tour title.
Henrik Bjornstad, who shared the second-round lead with Mulroy, stumbled to a one-over 73. That dropped him to minus-8, where he stands alongside Tyler Leon (69).
Mulroy birdied two and four before stumbling to a bogey on the sixth. He recovered that lost stroke with a 10-foot birdie putt on the par-4 seventh at Kinderlou Forest Golf Club.
He ran off five straight pars from the eighth and during that stretch would be joined by Tidland atop the leaderboard.
Tidland, the 2008 Boise Open winner, steadily climbed the leaderboard with birdies on two, five and seven. He dropped in back-to-back birdie efforts from the 10th to grab a share of the lead at 11 under.
However, Tidland stumbled to a bogey on the 12th, but suddenly was in the lead when Mulroy faltered to a double-bogey on the 14th. Both players birdied the 15th as Tidland stayed one shot ahead.
Tidland tripped to a bogey on the 17th to drop back to minus-10. He parred the last to end there.
'When the wind came up, my caddie was great at reading it all day,' Tidland stated. 'This is where you want to be going into the final round ' in the lead or close to it.'
Mulroy parred his final four holes to share the lead.
'I think this is the first time I've been in the 54-hole lead,' admitted Mulroy. 'The round was a little disappointing. I felt like I should have scored better on the back nine.'
Oskar Bergman posted a 4-under 68 Saturday to climb from a share of 31st into a tie for fifth. He was joined at 7-under-par 209 by Won Joon Lee (71), Kyle Reifers (72), Jay Delsing (71) and Paul Claxton (69).
Marco Dawson, Brad Elder, Kevin Johnson, Andrew Buckle, Guy Boros, Bradley Iles and J.J. Killeen are tied for 10th place at minus-6.