Triplett has 24 birdies, an eagle and 47 pars through 72 holes in the 90-hole tournament. Mickelson, making his 2004 debut, shot a 67 at Bermuda Dunes but still saw his two-shot lead evaporate. He won the Hope in 2002.
Kenny Perry, the 1995 champion, had consecutive eagles in his second 64 of the tournament and was one shot behind the co-leaders at 25-under 263.
Triplett who won the Reno-Tahoe Open last year for his second tour victory, holed a bunker shot for an eagle on No. 5 at Indian Wells Country Club, and made a twisting 20-foot birdie putt on No. 11 to highlight his fourth round.
John Daly had a rare double eagle on No. 2 at PGA West. Daly holed his second shot from 220 yards on the 514-yard par 5. He finished the round with a 72 and was 15 under.
Jay Haas, the 1988 champion and runner-up to Mike Weir a year ago, was two shots off the pace after a 67.
Perry gained four strokes to par with his consecutive eagles on the par-5 fifth and sixth holes at La Quinta Country Club.
He hit a 4-iron that stopped 12 feet past the hole on the 516-yard No. 5 and drilled the putt.
He hit another fine approach, a 3-iron from 229 yards on the 527-yard sixth hole. He curved the ball to the right and around a bunker, and the ball rolled within 8 feet. He sank that putt to pick up four shots in two holes and go to 24 under at that point.
Perry acknowledged the applause from the gallery with a wave, and shook his head, grinning.
Five others, including 2000 winner Jesper Parnevik at 266, were within four shots of the leaders.
Mickelson, making his 2004 debut and looking for his first win in 18 months, was somewhat inconsistent during his fourth round - ranging from a 40-foot birdie putt that he snaked into the hole to a drive into the water and a bogey on No. 10.
By comparison to Triplett's zero bogeys, Mickelson had four bogeys through the first 72 holes.
The first four rounds of the Hope are played as a pro-am on four courses, with the players alternating daily. The field was cut to the low-scoring 70 pros and ties for the final round at PGA West.
It took a 72-hole score of 277 - 11 under - or better to make the cut.
Scores traditionally are very low, with the desert courses relatively easy, and most of the par 5s reachable in two shots. Weir won at 30-under 330 last year, Mickelson also was 30 under a year earlier when he won a playoff with David Berganio Jr., and Joe Durant set a tour record for a 90-hole tournament with a 36-under 324 in 2001.
DIVOTS:@ There was a tribute to tournament namesake Bob Hope, who died last July at 100. A flyover by Air Force jets at PGA West ended the ceremony. ... Paul Azinger, who shot a fourth-round 69 and was 21 under, doesn't want Indian Wells Country Club, which has been rated the easiest course on the tour for the past three years, dropped from the Hope rotation. 'I would hate to see us move onto a longer course so golf and TV could be more boring,' he said.
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