Brown’s net favorability was +31 compared to +30 in May, virtually unchanged. Warren’s jumped from +10 in May (43 percent favorable to 33 percent unfavorable) to +19 today (52 percent favorable to 33 percent unfavorable).

Brown’s cross-over support also is waning. In May, 24 percent of Obama voters said they would cross parties to vote for Brown, but today 19 percent said they would cross over.

“The Democratic National Convention appears to have connected the dots for some voters in Massachusetts,” said Paleologos. “They’ve linked Barack Obama, Bill Clinton, Elizabeth Warren and Congressional candidate Joseph Kennedy, whose district includes Southeastern Mass. Warren benefited not only from her own speech, but from the oratory of others, both inside and outside of Massachusetts.”

One poll finding that could tip a close race back to Brown is the preference of general election voters of all parties for having one Democratic and one Republican Senator in Washington. Fifty percent said there is a benefit to having a member of each party representing Massachusetts in Washington DC, while 45 percent said it didn’t matter.