Senator Scott Brown has a new piece of evidence to bolster his argument that he is more than willing to cross party lines in the Senate.
Brown, a Republican who is locked in a tough reelection battle with Democrat Elizabeth Warren, is pointing to an analysis that found that, when the parties have split in the Senate, he has voted with Democrats 53 percent of the time since January 2011.
The analysis, based on data from Bloomberg Government, is just one of several surveys that have attempted to quantify how frequently Brown and others cross the aisle.
The review compared every vote in the 112th Congress when a majority of one party voted one way and a majority of the other party voted the other way. Bloomberg calls these “party unity votes’’ and they include parliamentary motions and legislative proposals where a majority of each parties’ members disagree. Votes that a member missed were not included in the calculation.
The analysis found that Susan Collins, a Maine Republican, crossed party lines most frequently and voted with Democrats 55 percent of the time. Brown, who voted with Democrats 53 percent of the time, was second on the list, followed by Olympia Snowe, a Maine Republican, who sided with Democrats 47 percent of the time and Lisa Murkowski, an Alaska Republican, who sided with Democrats 34 percent of the time.
Joe Manchin III of West Virginia was the Democrat who crossed party lines most frequently, siding with Republicans 27 percent of the time. He was followed by Ben Nelson, a Nebraska Democrat, who voted with the GOP 25 percent of the time, and Claire McCaskill, a Missouri Democrat, who voted with the GOP 23 percent of the time. John F. Kerry of Massachusetts, by contrast, voted with Republicans only 5 percent of the time.
Brown’s campaign argues the analysis shows Brown is effectively the most bipartisan member of the Senate because he and Snowe are closest to the 50/50 split. That argument seems bound to appear in Brown’s television ads and campaign rhetoric in the closing days of the race. He already alluded to the study during a campaign stop in Dorchester on Friday.
“I’m proud of my record of bipartisanship, and I will continue to be an independent voice for Massachusetts who always puts progress ahead of partisanship,’’ Brown said in a statement Monday. “During these challenging times, it takes moderate and independent voices to break through partisanship and make progress for our country.’’
In May, the Globe reported that, on the most important, news-generating votes since he arrived in office in early 2010, Brown joined Republican leaders 76 percent of the time, according to an analysis by Project Vote Smart, a nonpartisan organization.
Brown has often cited a Congressional Quarterly study that found that, in the year 2011, he was the second most bipartisan senator, behind Collins.
That study found Brown voted with his party 54 percent of the time and with President Obama’s stated positions 70 percent of the time. CQ’s count, like the Bloomberg analysis, tabulated only roll-call votes when Democrats and Republicans were at loggerheads.
The CQ study uses a different methodology than a Washington Post review that found that Brown voted with his party 66 percent of the time. The Post counted all votes, including many that had bipartisan support.