I find it annoying when someone says that Obama "has the most liberal voting record" when his record is similar to most of the other Democrats. The only difference is that he has a lot of NV (no votes) as, like McCain and Clinton, he has been campaigning.
Here is his actual voting record.
So the conservative National Journal compared Clinton and Obama. She was ranked 16th and he was ranked 1st in "liberal voting."
Guess how many times they voted differently? Twice. Does that really make Obama significantly more "liberal" than Clinton?
The hilarious thing is that Clinton voted against establishment of a Senate Office of Public Integrity while Obama and McCain voted for it's establishment.
The second vote they differed on was when she voted against allowing certain immigrants to stay in the United States while renewing their visas, while he voted for that.
That is it.
Now let's look at how often Senators voted with their party:
Here is the link for the 110th Congress.
Obama scores a 96.7% rating and Clinton scores a 97.2% rating. Humm, Obama must have voted with the Republicans more than Hillary. Seven Senators voted with their Party more often than Obama. I am sure it will surprise no one that Obama is a Democrat and votes that way.
The Democrat scoring lowest, in voting the party line, is Ben Nelson of Nebraska, with a 79.3% correlation to his party. The next worst is Landrieu and Bayh at 83%
Clearly most Democrats, and Republicans, vote predominantly along the party line. Republicans, surprisingly enough, have voted more often with Democrats than Democrats have voted with Republicans.
My conclusion is that calling Obama the "most liberal Senator" is either disingenuous or naive. It may make good political hay for the reactionary or uneducated masses, but it does not tell us much in terms of how liberal or conservative he is relative to other legislators.