A state bailout of the cash-strapped MBTA won the backing of 40 percent of Massachusetts voters in a new Boston Globe poll, outstripping those who said they would categorically oppose an infusion of aid. Support was most robust among those living inside Route 128, the T’s core service area. The statewide results, which showed 34 percent of respondents opposed using state dollars to plug the T’s budget gap and 26 percent were undecided or did not know, came as a surprise to analysts.