Who's the maverick?

Obama says he will bring change and a new nonpartisanship to Washington. McCain says he's the original maverick, and has the experience to prove it. Biden says McCain voted with President Bush 95% of the time; he's no maverick. The Republicans say Barack has no record of acting bipartisan in Washington.

Who's right?

The problem with cherry-picking data is it feeds into the old adage that students so often like to cite: "You can make statistics say anything."

Biden's statistics are correct: in 2007, John McCain supported President Bush 95% when the president announced a stand on a Senate roll call vote. This is according to the presidential support scores calculated by Congressional Quarterly annually, and used by political scientists who study both institutions. Unfortunately, this does not necessary answer the question of whether McCain is a maverick or not. Some media accounts report that there were a lot of immigration votes that year. It just so happened that Bush and McCain agreed on immigration: the problem was, the rest of the party left them hanging dry. Presidential support scores are problematic because they take a small subset of Senate roll call votes and don't give a good sense of whether someone is willing to buck the party.

Instead, I recommend looking at the party unity score--also calculated by Congressional Quarterly. This score is defined as the percentage of the time the member of Congress voted with their party when 50 percent of the party voted one way and 50 percent of the other party voted the other way (or vice versa).

For example, a party unity vote has to have at least half the Republicans voting nay on an issue and half the Democrats voting yea to be considered in the analysis. This eliminates procedural votes and commemorative legislation that often passes with overwhelming partisan majorities. This gives us a better look at who is willing to buck the party on a number of issues, whether the president takes a stand or not.

Here's a chart of McCain's Party Unity Averages by Congressional session, beginning with the 100th Senate and ending with the 109th. Next to McCain's score, you'll see the Republican Senate average for that session:

Congress McCain GOP Average
100 88 77
101 84 78
102 88 83
103 91 84
104 91 91
105 84 87
106 87 90
107 71 86
108 84 92
109 81 89

Like many members of Congress, McCain voted more often with the party early his career began to become more independent the longer he served. Indeed, we begin to see this drift during the 105th Congress (1997-1998). Three times, McCain's party unity average is almost a full standard deviation below the Republican mean: in the 107th, 108th, and 109th Congresses.

McCain is no Ralph Hall (who exhibited party unity scores in the 20s and 30s as a Democratic Representative from Texas in the House. He later switched parties and became a Republican). But he's clearly NOT the party unity poster boy Biden's comments make him out to be.

Now, what about Obama? Well, I only have data from the 109th Congress available to me. The Democratic party unity average in that session was 89 percent. Senator Obama's average was 96 percent. This suggests there is some truth to McCain's claim that he has the record of a maverick and Obama does not. Even Obama's running mate rated a 90 percent in the 109th Congress.

Now whether you knew McCain was a maverick from last night's speech, that's a different story.

Next time, I hope to do an analysis of pre-VP nomination experience to evaluate the claim that Palin has precious little experience compared to other past nominees.