National Journal has assembled an excellent graphic that details which senators have crossed party lines the most frequently on the $410 billion 2009 spending bill. That measure is expected to become law by mid-week but has sparked nagging questions about Democratic party unity from the Beltway media.

It may not surprise many political junkies, but Sen. Evan Bayh (IN) is the Democrat who has crossed party lines most often on the spending bill, voting with the GOP eight times since debate on the legislation began last week. (Sen. Olympia Snowe [R-ME] mirrors him on the Republican side, voting alongside Democrats eight times during the process.)

But that's not the only National Journal study that deems Bayh his party's most conservative senator. When the magazine's annual vote rankings came out a few weeks ago, Bayh was ranked 51st in the Senate on a composite score of liberalism -- placing him ahead of former Democratic Sen. Joe Lieberman (I-CT), who placed 43rd, as well as Snowe, who was No. 47, and Collins, who was No. 50.

Now, the National Journal rankings are no ordinary congressional vote study. After then-candidate Barack Obama was ranked the most liberal senator for 2007, the GOP had a field day using the statistic for attack lines on the presidential campaign trail.

It appears that Bayh is emerging as his party's most vocal centrist ... and just in time for the budget debate to heat up.