I've had limited experience in this matter, but I did write to a Republican Senator from CT during the Lewinsky thing asking for him to express concern about privacy issues, and he paraphrased my on the Senate floor. It was (as you may recall) a 'no impact' statement as far as the final results were concerned.

To that end Republicans in moderate to liberal states, or who are otherwise not in lockstep with the party include:
Wayne Allard (CO)
Lamar Alexander (TN)
Lincoln Chafee (RI)
Susan Collins (ME)
Mike DeWine (OH)
Pete Domenici (NM)
Chuck Grassley (IA)
Judd Gregg (NH)
Jim Jeffords (VT) not a Republican
Richar Lugar (IN)
John McCain (AZ)
Gordon Smith (OR)
Olympia Snowe (ME)
Arlen Specter (PA)
John Sununu (NH)