As Mahan reduced McDowell's advantage to one after 15, tension was nearing fever-pitch.
Molinari sent his putt just short of the hole on 18, leaving Fowler with an 18-footer to halve the match, and he displayed nerves of steel to rattle it in.
It finished all square, making it 13-1/2 - 12-1/2, then Zach Johnson saw out his game against Harrington 3&2.
It tied the match at 13-1/2 - 13-1/2, leaving it all down to McDowell and Mahan in the one game still out on the course.
McDowell needed a win for Europe to taste Ryder Cup glory - Mahan required just a half for a successful United States' defence - as they walked down the 16th.
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