By Jon Keller, WBZ-TVBy Jon Keller

BOSTON (CBS) – It’s official.  Congressman Ed Markey (D-Seventh District) is the first Democrat to announce his candidacy for the U.S. Senate seat to be vacated if and when John Kerry is confirmed as Secretary of State.

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In a statement this afternoon, Markey says in part: “I have decided to run for the U.S. Senate because this fight is too important. There is so much at stake. I refuse to allow the Tea Party-dominated Republican Party to lead us off the fiscal cliff and into recession. I won’t allow the NRA to obstruct an assault weapons ban yet again. I will not sit back and allow oil and coal industry lobbyists to thwart our clean energy future or extremists to restrict women’s rights and health care.”

The 66-year-old Markey was first elected to Congress in 1976 as part of a wave of post-Watergate reps, and is the dean of the New England and Massachusetts House delegations, ninth overall in seniority. He famously dropped out of the 1984 Senate race at the last moment to seek re-election to the House.

Markey’s quick entrance should have a major impact on the emerging field in the U.S. Senate race.

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For instance, he and Rep. Mike Capuano share some of the same financial and political supporters, but Markey has been at it longer and his candidacy may trump Capuano’s aspirations. And along with money and DC stature, Markey brings to the table a Middlesex County and Metrowest base that could also scare off other contenders.

A double Eagle (Boston College and BC Law), Markey is a genial backslapper who should wear well with Democratic primary voters.

The downside: outside of the Seventh District, his name-recognition is surely low, and as a 30-year denizen of the Beltway who essentially maintains a mail drop here, he may have to shake off the taint of DC insider-dom.

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Jon Keller