Through two rounds, Tim Jackson has taken just 51 putts because he's put himself in good spots on the greens. (John Mummert/USGA)

Carmel, Ind. - This has been a golf season filled with surprises. An Argentinean won the Masters. The final round of the U.S. Open was completed on a Monday. A 59 year old came within a playoff of winning the British Open and a 33 year old named Tiger Woods missed the cut.

Strange days have found us. So why should things change be any different at the U.S. Senior Open this week? Why shouldn't Tim Jackson pull off the biggest surprise of all?

"Amazing an amateur's doing that," said Fred Funk, who is among those hot on Jackson's heels. "I heard he just turned 50 and has put himself in this position, just keeps hammering down birdies. So he's doing a great job."

Jackson, the 50-year-old amateur playing in his first U.S. Open of any kind – regular or senior – continued his flirtation with history on Friday morning at Crooked Stick Golf Club. After a first-round 66 put him in a tie for the lead, Jackson upped the ante with a 5-under-par 67 to take the point outright at 11 under in the 30th playing of the championship.

An amateur has never won the title. William C. Campbell finished second at Winged Foot in 1980, the closest any have come. In fact, the last amateur to win a USGA of any kind occurred in 1967 at the U.S. Women's Open when Catherine Lacoste did it.

"I know there will be rough patches," said Jackson, who has his 15-year-old son, Austin, as his caddie. "It's been all popsicles and lollipops so far, but I expect there to be some tough spots. Hopefully, we can keep a level head and work through them."

Playing the two nines in conventional order, Jackson got to 11 under before suffering his first bogey of the week at Crooked Stick's toughest championship hole, No. 16. But after missing the fairway at 18, Jackson fired an 8-iron from 172 yards to 5 feet of the flag and rolled it in for a closing birdie.

While his second round wasn't nearly as tidy as his first – he missed eight-of-14 fairways – Jackson' iron play was outstanding and he needed just 26 putts. Over two days, he has putted just 51 times.

"The one thing I have done consistently is I've adopted a routine and I have not deviated from it," said Jackson, who did not begin playing competitive golf until he was 26. "And it just has totally freed me up to not be too concerned about the line. I've just been focusing more or less on the pace, and I've putted really nicely this week."

As the morning wave finished up, the two-time U.S. Mid-Amateur champ (1994 and 2001) enjoyed a two-stroke lead over Funk, a Champions Tour major winner and eight-time PGA Tour champion. The threesome who shared the lead with Jackson after Friday – Dan Forsman, Greg Norman and Joey Sindelar - were in the afternoon wave and began their trip at six under par.

Another surprising performer, pro Robin Freeman, reached six under for the Senior Open with a second-round 68. Also playing in his first Senior Open, the 50-year-old Freeman is the only player to be medalist at the PGA Tour Qualifying Tournament twice. But he has never won a PGA Tour event.

"I haven't played well lately in my career, over the past, I don't know ... 20 years," deadpanned Freeman, who has two Nike Tour victories to his credit. "No, but it's been a struggle for me lately playing golf, and it's good to get some good play going.

Among other players to complete their second rounds, former U.S. Amateur champion Mark O'Meara moved up the board with a 69 to get to five under for the week, rubbing elbows with Bob Tway, whose 69 took him to the same place. Scott Simpson, winner of the 1987 U.S. Open, was one shot farther back at four under after a second-round 72.

Given Jackson is from suburban Memphis, perhaps it's not all that stunning to see him leading at Crooked Stick. After all, another Memphis-connected player – John Daly – did pretty well here in 1991 at the PGA Championship.

"Just having my son caddieing and the family here, it's been very special," Jackson said. "Regardless of what happens the rest of the week, these memories of the last couple of days and the fans pulling for you are just wonderful."

Phillip Howley is a freelance writer whose work has previously appeared on www.ussenioropen.com.