Here are the ACLU lifetime ratings of the major party candidates still in the race:
Barack Hussein Obama (D) 82%
Hillary Diane Rodham Clinton (D) 75%
Ronald Ernest "Ron" Paul (R) 61%
John Sidney McCain III (R) 25%
Note: I have been unable to find ACLU ratings on Maurice Robert "Mike" Gravel (D), who was was in the Senate from 1969-1981, and Michael Dale Huckabee (R), who served 10 years as governor of Arkansas. I would be very interested any any data (with sources) regarding their ratings. I will say that I suspect they rate Gravel very high, and Huckabee in the same range as McCain.
So, there you go.
The ACLU rates Obama, Clinton, and Paul highest of the four remaining candidates that are currently in Congress.
And McCain the lowest.