Campbell maintains form

The 34-year-old Texan, who kicked off the tournament with a 65 which had promised to be so much better before he bogeyed the last two holes, birdied the second with a sublime pitch to three feet.

A two on the 240-yard fourth for the second day running took him back to nine under and then he birdied the long eighth as well for an outward 33. The 495-yard 10th held no fears for him either as he birdied that too to improve to 11 under.

Chasing the first major of his career - he was runner-up to Shaun Micheel in the 2003 US PGA championship and third in the 2006 Masters - Campbell has not had a top-10 finish on the US Tour in his last seven starts.

Ryder Cup team-mates Jim Furyk and Kenny Perry and former Open champion Todd Hamilton were his closest challengers on six under, while Tiger Woods remained only two under after four holes of his round.

Padraig Harrington, three under overnight, was among the later starters, but Northern Ireland's Graeme McDowell continued his impressive performance when he climbed to five under and joint fourth prior to bogeying the short 12th.

McDowell, whose one previous Masters appearance was four years ago, had reached five under on the opening day before bogeying the 17th and 18th like Campbell.

He came out again just after 8.30am, birdied the long second and then made amends for a bogey on the seventh by picking up more strokes at the ninth and 10th.

After saving par on the next from six feet - his approach finished just above a bunker - he pulled his tee shot to the 12th, sent his chip 10 feet past and missed.

He hit a couple of loose tee shots on the last two holes and paid the price for them but generally hit the ball well and into all the right places.