You may have seen this coming, but Politix is surprised.
Why's this a surprise? Well, everyone thought Republicans were plotting to get Brown into Kerry's Senate seat, after Brown lost his own seat to Democrat Elizabeth Warren in 2012. Indeed, conspiracy theorists (and some leading journalists) thought Republican attacks on Susan Rice over Benghazi were a purely political ploy designed to get Kerry made Sec. of State and free up his seat.
Some pundits are calling this bad news for the GOP, but Politico speculates that instead Brown plans to run for Bay State governor in 2013.