Romney was the fourth republican governor in a row there, the problem is that he was so lousy that he slinked out of office with a 34% approval rate, and gave the office to the democrats.
Unfortunately you’ve got it exactly right re: Romney in MA.
I am intrigued by the lack of polling data on this race, however. Could it be closer than the usual Democrat suspects want to acknowledge? This is an exceedingly rare open Senate seat for them, and absolutely no polling is being reported.