The reigning Order of Merit champion birdied No. 18 on Saturday to take a one-shot lead over three players heading into the final round at the Abu Dhabi Golf Championship.
Harrington, who secured the Order of Merit title on the final day last season, shot a 4-under 68 and is at 13-under-par 203 through three rounds.
'Although it can make you a little bit protective, it's less stressful than chasing,' the Irishman described leading.
'It would be a big pleasure and quite a surprise to win here. I'd be thrilled with that. In fact, I'm thrilled that I'm well ahead of where I thought I would be at this stage of the year. It's a nice position.'
Trailing Harrington by a shot at 12-under 204 are Miguel Angel Jimenez (68), Peter Hanson (66) and Shiv Kapur (68). They are among nine players who are within three shots of Harrington's lead.
Among that group, second-round leader Phillip Price is alone in fifth place at 11-under 205 following a 71. Retief Goosen (68) and Paul Casey (67) lead a group of five players who are tied for sixth place at 206.
Harrington had five birdies and just one bogey Saturday and shot a 34 on both sides. He opened with back-to-back birdies at the first two holes, added another birdie at No. 4 and then dropped his only shot at the eighth.
When he birdied No. 12, Harrington tied Price for the lead at 12 under. They were soon joined by Hanson and later by Jimenez.
But while Price stumbled to a pair of costly bogeys, Harrington bided his time with pars until he was able to take the lead with an 8-foot birdie putt at the last.
Among the players who were at 12-under late in the round, only Jimenez failed to birdie the 18th.
Closing that strongly on Sunday might be the only way to catch Harrington. If there are players in the field who can do it, certainly they lie among those who challenged him Saturday.
'I've done particularly well for three rounds and haven't seen the scoreboard until the 18th green each day, so I certainly won't be looking at one individual out there,' Harrington said.
'I will be looking at only one individual and that will be me. I won't worry about anyone else.'
Alastair Forsyth (69), Thongchai Jaidee (67) and Jean-Francois Lucquin (67) are tied with Goosen and Casey at 10 under. Defending champion Chris DiMarco (68) leads a group of four players who are knotted in 11th place at 9-under 207.