According to http://politifact.org/truth-o-meter/ (I crunched the numbers)

McCain statements (151 evaluated) 45% were lies (Barely true to Pants on fire lies)
Palin statements (20 evaluated) 35% were lies

Obama statements (154) 29% were lies
Biden statements (33) 39% were lies

Egregious lies (False and Pants on Fire)

McCain: 27%
Palin: 20%
Obama: 18%
Biden: 21%

The data
McCain Palin Obama Biden
True 29 6 49 8
Mostly True 27 2 29 5
Half True 27 5 31 7
Barely True 27 3 18 6
False 34 2 25 5
Pants on Fire 7 2 2 2
Total Statements 151 20 154 33

By Pct McCain Palin Obama Biden
True 19.21 30 31.82 24.24
Mostly True 17.88 10 18.83 15.15
Half True 17.88 25 20.13 21.21
Barely True 17.88 15 11.69 18.18
False 22.52 10 16.23 15.15
Pants on Fire 4.64 10 1.3 6.06
Total Lies (False+pants) 27.15 20 17.53 21.21
Mostly Lies (False+Pants+Barely) 45.03 35 29.22 39.39