Mickelson and Fred Couples will each be trying for their second Masters title when they begin their final round Sunday at Augusta National.
A lot happened after the third round resumed Sunday morning following a four- hour weather delay and the eventual suspension of play Saturday night.
Mickelson made the most of it, playing the last 13 holes of his round at one- under and moving to four-under-par 212 overall after a round of 70.
'To be in the final group and have a chance -- it's pressure, but it's a dream,' said Mickelson, who broke through with his first major win here in 2004.
Couples moved one shot further into red numbers after the re-start and is at 3-under-par 213 after a 72. The 1992 champion is tied for second place with second-round leader Chad Campbell, who struggled to a 75.
'I feel great. I haven't played 31 holes in a long time, but I'll go home and rest and start again like it's a new day,' said Couples, who at 46 years old made his 22nd consecutive cut at The Masters.
The last 15 Masters winners have played in the final pairing.
'I put no credence in it when I was trailing,' Mickelson said of that trivia tidbit, 'but now that I'm leading, I like that stat.'
Among those tied for fourth place at 2 under is defending champion Tiger Woods, who struggled through a bad stretch on his back nine to finish the third round with a 1-under 71.
Vijay Singh (73) and Rocco Mediate (73) are also tied for fourth. Mediate missed a chance to play in the final pairing when he double-bogeyed 18.