U. S. Rep. Edward Markey, the dean of the Massachusetts Congressional delegation, announced his intention Thursday afternoon to run for the United States Senate if John Kerry is confirmed, as expected, as the nation’s next secretary of state.

“The events of the last several weeks – from the devastation of Hurricane Sandy and the tragedy at Sandy Hook Elementary to the fiscal cliff debate over tax giveaways to the rich, have all made clear that Massachusetts needs a Senator with the right priorities and values. I have decided to run for the U.S. Senate because this fight is too important. There is so much at stake," Markey said in a statement.

Markey, 66, has served 18 terms in the House of Representatives after first being elected to Congress from Malden in 1976. In November, he was re-elected to another two-year term in the newly configured 5th Congressional district, and would not have to give up his seat for run for the Senate in a special election.

With Congressional leaders and President Obama trying to broker a deal to avoid automatically triggered tax increases and spending cuts from taking effect on Jan. 1, Markey said he feels as though “we are fighting the same old Republican Party” and a GOP agenda “that benefits only the powerful and well-connected.”

“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,” Markey said.

The Congressman called for investments in innovation and jobs, protection for Social Security and Medicare, a “sane approach” to gun violence, and a strategy to curb carbon pollution and global warming that also moves the country toward energy independence.

Markey, who put energy and environmental protection issues at the forefront of his agenda in Congress, is the ranking Democrat on the Natural Resources Committee, and from 2007 to 2010 chaired the Select Committee on Energy Independence and Global Warming. He served two terms in the Massachusetts House representing Malden and Melrose before his election to Congress.

According to his latest campaign finance filings with the Federal Elections Commission, Markey had over $3.1 million in cash-on-hand at the end of November that could be put toward a Senate campaign. U.S. Rep. Michael Capuano, U.S. Rep. Stephen Lynch and U.S. Rep. Niki Tsongas are considering whether to run for the Senate.

With his announcement Thursday, Markey became the first Democrat to formally enter the fray and will bring into the contest more than a generation of experience in Washington as well as a long voting record.

State Sen. Benjamin Downing (D-Pittsfield) is also eyeing a possible run, promoting himself as satisfying a desire among voters for “new voices and new ideas.”

President Obama last Friday announced his nomination of Kerry to succeed Hillary Clinton as secretary of state. Once Kerry resigns after his confirmation, Gov. Deval Patrick would have to set the date for a special election within 145 to 160 days. The governor also gets to appoint an interim senator until the special election can be held, and he has said he favors finding an interim appointee that could serve as a placeholder without any desires to run for the permanent post.

Markey ran for Senate in 1984 for the seat vacated by the late Sen. Paul Tsongas, but eventually dropped out of that race before the primary. Kerry went on to win the election and hold the seat for the next 28 years.

U.S. Sen. Scott Brown is widely considered to be the leading contender on the Republican side of the ticket, should he decide to run again after losing by eight points in November to Sen.-elect Elizabeth Warren. Brown has not yet commented on his plans for another special election after capitalizing on the last special election in 2010 to score a surprising victory after the death of Sen. Edward Kennedy.

Kennedy’s son Edward Kennedy Jr. briefly mulled moving back to Massachusetts from Connecticut to run for the U.S. Senate, but announced before Christmas that he had decided against a campaign.