The Republican Party's newest rising star, Sen. Scott Brown of Massachusetts, voted with the Democrats to break a GOP filibuster of Majority Leader Harry Reid's $15 billion jobs-creation bill. After Brown announced what he was doing, four other Republicans joined him. (Watch a report about Scott Brown crossing the aisle.) Why is Brown breaking ranks with the GOP on only his second vote as a senator? Here are five possible explanations:

1. Brown's a Republican In Name Only (RINO), after all: When he was running to replace "liberal lion" Ted Kennedy, says blogger Michelle Malkin. Scott Brown was the darling of the Tea Party movement and conservatives alike. But he was always more moderate than his fans. "I feel like a sucker," says conservative Don Surber at the Charleston, W.Va., Daily Mail. "We’ve been tea-bagged."

2. He's earning his "independent" billing, cheaply: Brown owes his election to "the left-leaning indies back home," says Allahpundit at Hot Air. He ran as an "independent voice," and bucking his party leadership to pass a relatively small package of small-business tax cuts is a low-cost way to prove it.

3. Brown is the new bipartisanship: Brown's election was supposed to stymie Democrats by killing their supermajority, says Nate Silver at FiveThirtyEight. But as this vote shows, it may have actually opened the way for him and the two other "authentically moderate" Republicans — Olympia Snowe and Susan Collins — to cross the aisle on popular bills.

4. Moderates tend to back useless bills: Don't read too much into Scott Brown's support for a "scrap of a bill" centered on tax cuts, says Bill Scher in The Huffington Post. Yes, a few Republicans still have "some interest in legislating instead of constant obstructing," but they only seem to back bills that have been "shrunk down" to nothing in the interests of bipartisanship.

5. Brown just hasn't been tainted by Washington yet: This should have been an easy bill to pass, says Dana Milbank in The Washington Post. It only became a "pointless snarl" thanks to partisan political calculations. Brown's willingness to vote for the bill just shows he "hasn't been in Washington long enough to be intoxicated by the Spirit of Party."


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