No surprise, but still gratifying. As of this morning, Charlie Cook had MA-10 rated a likely Democratic hold. Tonight, I’m not so sure.

“It’s got nothing to do with politics,” the Quincy Democrat said today. “Life is about change. I think it’s healthy. It’s time.”

The 68-year-old lawmaker said he has been considering leaving the House for several years, but was talked out of it two years ago by the late Senator Edward M. Kennedy, who convinced his friend he should stay and help President Obama with his first-term agenda.

“He said, ‘Come on — this is a new time. It’s a new era. We [will] have a new president. We’re all needed,” Delahunt recalled Kennedy telling him…

Many Democrats — including House Speaker Nancy Pelosi and House Majority Leader Steny Hoyer — urged Delahunt to stay another term, worried that the volatile campaign environment could give the GOP a chance at the seat. Joseph P. Kennedy III’s decision earlier this week not to seek the seat makes Democrats even more nervous.

Thanks to that new president, come November, he won’t be needed anymore. Delahunt had a tough road to reelection: He had formidable challengers, his district broke for Scott Brown by a wider margin than any other in Massachusetts, and his handling of Amy Bishop’s shooting of her brother in 1986 when he was the local D.A. is under investigation. Oh, and he’s been known to refer to Hugo Chavez as his “excellent friend.” He also voted for Pelosi’s ObamaCare bill in November, so there’s no risk that retirement will make him more favorable to it this time.

Anything can happen in the Bay State this year — just ask Martha Coakley — but this looks like a plum pick-up opportunity. Exit question: Will Joe Kennedy III jump in now? I’ll bet Madam Speaker’s on the phone with him as we speak…