Two hundred and thirty-one days. That's how long Tiger Woods has been waiting for today to come.

Since Aug. 20, when Woods won the PGA Championship, he's been thinking of winning today's 65th Masters.

Not because it would be his second Masters victory. Rather, it would mean a record fourth straight major championship title.

On this day of reckoning for Woods, the world's No. 1-ranked player leads by one shot over Phil Mickelson, who happens to be the No. 2 player in the world. If Mickelson wins, he'll be only the second left-handed golfer to win a major championship. Bob Charles won the 1963 British Open.

Thanks to a 4-under-par 68 on Saturday that followed rounds of 70-66, Woods is at 12-under-par 204 for three trips over the Augusta National Golf Club. Mickelson has shot 67-69-69.

Woods, who birdied Nos. 13-15 to take the lead Saturday, tops the field in driving distance (306.5 yards) and greens in regulation (47 of 54). He's tied for 39th in putting, with 93 putts.

If the 25-year-old Woods wins today to hold all four majors at one time, he will call it the Grand Slam, though by definition a slam must occur in a calendar year. Everyone else will call it amazing.

As a front-runner, Woods is tough to beat, holding a 20-2 record on the PGA Tour, including major championships. He's been the 54-hole leader in all five of his major championship victories.

"I'm looking forward to the challenge," Mickelson said.

"Tiger is a human being just like the rest of us, and he's going to be out there nervous also," said Mark Calcavecchia, one of Woods' best friends on the tour, who is two shots back. "However, he is the best in the world and he has that going for him."

"Obviously, Tiger, he's Tiger and he's not going to back down," said Ernie Els, who is three shots back. "He's the danger man out there. But there's a lot of talent on that leaderboard."

Woods, who was winless for six months before winning the Bay Hill Invitational three weeks ago, is playing like the top player in the game. He has won his past two starts but would like a little more cushion than he has Sunday.

"This is not the way I would have scripted it," Woods said. "I'd like to be leading by 10."

The only tournaments Woods has lost after being the overnight leader are the 1996 Quad Cities Open and the 2000 Tour Championship. In the Tour Championship, Woods was bidding to become the first golfer to win 10 tour events in a season. Mickelson outdueled him for the victory.

It was also Mickelson who beat Woods in the 2000 Buick Invitational, ending Woods' streak of six consecutive victories.

"I have a lot of respect for Tiger as a player and a person," Mickelson said. "With that being said, I've been able to go head-to-head with him and come out on top a few times. I do have confidence that I can prevail.

"For me to win, I have to strive to reach a different level of play. I have to be able to attain it."

"Phil is obviously, as everyone knows, a great player," Woods said. "He and I have a wonderful chance, but you can't go out there and just think it's Phil and myself. If you look at that board, there are some guys who have won some serious tournaments around the world."

Mickelson likes his position, not only on the leaderboard, but on the course Sunday. Because he birdied the final two holes to move into second place, he's paired with Woods in the final group of the day.

"I knew heading into No. 17 that I needed to birdie 17 and 18 to get in the last group, and I felt like that would be important," Mickelson said.

In mid-March, Mickelson had already finished his final round in the Bay Hill Invitational and had to watch as Woods birdied two of the final three holes to beat him by a shot.

"I didn't want that to happen again," Mickelson said. "I wanted to be playing with him and know where we stand and not only that, know where the rest of the field stands, because there's a lot of guys who potentially could win this tournament."

They include Chris DiMarco and Calcavecchia. DiMarco, the first- and second-round leader this week, and Calcavecchia, a birdie machine, are two shots back.

DiMarco has turned in rounds of 65-69-72 to tie the record for lowest score through 54 holes by a Masters rookie. With a win today, he would be the fourth golfer in Masters history to win the tournament in his first appearance.

Calcavecchia, who broke the PGA Tour 72-hole scoring record earlier this season, has fired rounds of 72-66-68. Calcavecchia shares the Masters record for lowest score on the back nine, a 7-under-par 29 in 1992.

DiMarco and Calcavecchia, who are former University of Florida golfers and use an unorthodox putting grip they call the claw, are paired today in the second-to-last group of the day.

"He's a [Florida] Gator, I'm a Gator and we're going to be clawing it together all day," DiMarco said of Calcavecchia. "He's a free-going guy. He's going to be swinging for the fences. That's my goal -- to be a little bit more aggressive on the par-5s."

Els, the Masters runner-up last year, is three shots back, along with David Duval and Argentina's Angel Cabrera. Els shot 68 on Saturday, and Duval and Cabrera had 70s.

Other golfers within striking distance, four shots back, are Rocco Mediate (66 Saturday) and Kirk Triplett (70). Golfers five back are two-time Masters champion Jose Maria Olazabal (71), Brad Faxon (68), Lee Janzen (72) and Steve Stricker (72).

Of the players within five shots of Woods, only Els, Olazabal and Janzen have won major championships. Olazabal has two Masters titles, and Els and Janzen are two-time U.S. Open winners.

Mickelson would love to add his name to that list of major players. He's 0-for-34 in major championships.

"I desperately want this," Mickelson said. "I've said all along that I feel this [tournament] provides me with the best opportunity, and it is something that I've been looking forward to for some time, to finally break through."

For three days, Woods has plotted his way around the Augusta National Golf Club, hoping to give himself a shot at four in a row. He was tied for 15th after the first round, moved into a tie for second after 36 holes and now leads by one after 54 holes.

"I didn't really do anything great," Woods said of his five-birdie, one bogey round Saturday. "I just plodded my way along. That's basically how I played and how I've played all week."

"He hits it so far, literally par is 68 for him," said DiMarco, who played with Woods on Saturday. "The par-5s are just long par-4s for him. The reason he's so good is it doesn't look like he does anything and he shoots 68."