Barry Lane is alone in fourth place at 5-under-par, followed by Colin Montgomerie (68) and Joakim Haeggman (71), who share fifth at minus 4.
Harrington bogeyed the 17th hole Saturday to fall to 4-under-par but rebounded in a big way at the par-5 18th. He bombed his drive down the fairway and was left with only a 6-iron into the green, which he played to six feet. Harrington ran home the eagle putt to reach 6-under-par and share the lead with Campbell.
'That was important to me,' said crowd favorite Harrington. 'After not birdieing the 16th and bogeying the 17th I would have been frustrated because I had a lot of chances today but I stayed patient and got rewarded on the last.'
Campbell quickly grabbed the lead back at the par-5 16th when he wedged his third shot to three feet to set up birdie. Campbell nailed his approach over the green at the 17th and tried to chip his third shot left of the hole but the ball ran through the green and nestled on the front fringe leaving him 40 feet to the cup.
Campbell chipped close and tapped in for the bogey to fall back into a tie for the lead. While Campbell was bogeying 17, Lawrie in the group ahead narrowly missed a 30-foot eagle putt at 18 but settled for birdie and joined Campbell and Harrington at minus 6.
The New Zealander hit another long approach at 18 when he roped a fairway-wood over the green. Campbell chipped 15 feet past the hole but drained the putt to take back the lead and put himself in the final group Sunday.
'It was frustrating for me today,' said Campbell, who last won on the European Tour at the 2001 Heineken Classic. 'I played well from tee to green but missed a lot of putts coming home. The putt on the last was nice to lead the tournament with 18 holes to play. I had a lot of opportunities but didn't convert them. Hopefully tomorrow it will it will be my turn.'
One of the major factors that Campbell will have to contend with Sunday is playing with Harrington, who will have a decided home-field advantage.
'It is going to be a great day for everyone out there tomorrow, especially the spectators,' said Campbell. 'Having played the New Zealand Open for the past seven years I can understand why Padraig is playing so well, like Darren Clarke did last year. He will have the home support but the Irish people are very knowledgeable about the game of golf and respect all the players so it will be fun tomorrow.'
'This is a big event in a European context but means more because it is at home, only half an hour from where I grew up, so there's more to it than just the European Open,' said Harrington, who posted his second 69 in as many days.
Lawrie also shot a 3-under 69 Saturday and is in position for his first victory since last year's Dunhill Links Championship. Over the last three holes, Lawrie had putts that skimmed the cup and could have easily given him the 54-hole lead.
'I played beautiful today,' said Lawrie. 'I hit one bad shot off the first and that was it. The last nine holes I made two birdies and missed a putt on pretty much every green. All good putts, all dead pace.'
Paul Casey is alone in seventh at 3-under-par. Ian Woosnam and American Fred Funk shared low round of the day honors with 5-under 67s. The pair are part of a group tied for eighth place at minus 2.
Full-field scores from the Smurfit European Open