'I'm having some breaks. I'm getting up and down when I need to,' Lancaster said. 'You have got to have breaks to win any golf tournament, I don't care who you are. They say you make your breaks, but you can't make anything happen out there. What's going to happen is going to happen.'
Billy Andrade, who held a share of the overnight lead with Lancaster, carded a 2-under 70 to finish alongside Steve Flesch (65), Vijay Singh (66), Justin Leonard (66) and Grant Waite (69).
Lancaster was flawless Saturday at Angus Glen. He opened with a 12-foot birdie at the first and picked up two additional birdies on the front nine to make the turn one-shot clear of the field at 14-under.
The 39-year-old continued his fine play on the inward nine with a 15-foot birdie at the 11th. At the par-5 16th, Lancaster reached the green in two with a seven-iron and had a 15-foot putt left for eagle but left it short. He made the second putt for birdie, however, to open a two-shot lead.
Lancaster had an opportunity to put more distance between himself and the field but he failed to convert a birdie chance at the par-4 18th.
'I actually feel like I'm a little disappointed,' said Lancaster, whose best finish in 2002 is a tie for fifth at the Western Open. 'I scored well again and today I finally struck the ball well and I was a little disappointed, I actually missed a short putt on the last hole.'
Lancaster is seeking his first PGA Tour victory since he came out of a six-man playoff to capture the 1994 Byron Nelson Classic. The last time Lancaster took a lead into the final round was at the 1996 Nissan Open, where he struggled with a closing 77 to finish five shots back.
'My caddie, he's starting to get wound up so tight. I'm calming him down,' said Lancaster, who posted a top-10 finish at this event in 1991. 'We have to be more relaxed tomorrow. I guess the biggest thing I've got to do, I have to believe I can do it. That's the hardest part for me, not believing in myself.
'Being in this position, and I've been there a lot this year, I'm starting to understand how hard it is to win. But then I'm also starting to understand I don't have to be perfect to win.'
Chalmers, who picked up two eagles on the front nine over a span of three holes, matched Lancaster with a birdie at the 10th and played steadily to keep pace.
'I really played quite nicely. I got a good solid start and really the eagles on the front nine were the backbone of my round and got things moving in the right direction,' said the Australian. 'I'm very pleased with the way I played and the way I handled myself.'
Frank Nobilo posted a 5-under 67 to finish alone in eighth at 12-under-par 204. Jeff Sluman, whose round of 66 featured two eagles, was next at 11-under.
Gene Sauers, who earned his first win since 1989 at last week's Air Canada Championship, shot a 67 to join Geoff Ogilvy and Canadian Ian Leggatt in a tie for 10th at 10-under-par 206.
Full-field scores from the Bell Canadian Open