(CNN) - Rep. Ed Markey of Massachusetts said Thursday he will seek the U.S. Senate seat currently held by Sen. John Kerry, who was nominated to become the next secretary of state last week.
"I have decided to run for the U.S. Senate because this fight is too important," he wrote in an email to people who signed up for updates from his Senate website. "There is so much at stake. We need a senator who will work with President Obama, and anyone else, to move our country and our Commonwealth forward."
The Democratic congressman is the most senior member of the Massachusetts delegation and was elected to his 19th term in November.
President Barack Obama nominated Kerry on Friday to serve as his next secretary of state, and Kerry is expected to be confirmed easily by the Senate.
Two possible contenders - Ted Kennedy Jr., the eldest son of the late senator, and actor Ben Affleck - considered a bid for Kerry's seat, but have recently said they will not run.
Markey is said to have considered running for the seat in 1984 upon the retirement of Sen. Paul Tsongas. But he did not run, and the seat was won that year by Kerry.
Other Democratic contenders could include Reps. Michael Capuano and Stephen Lynch. Sen. Scott Brown, who was elected in a 2010 special election but lost his re-election bid this year, is considered a possible candidate on the Republican side.
After Markey's announcement, Lynch said in a statement: "I look forward to Senator Kerry's confirmation as our next Secretary of State. Once confirmed, we will need to fill the vacancy and keep a strong voice in the Senate on behalf of Massachusetts families. While I am giving serious thought to running for the U.S. Senate and have received great encouragement, at this point I am still focused on my job as a Congressman and am working with my colleagues in the Massachusetts delegation to find solutions to the fiscal cliff."
Markey wrote, "We need to invest in innovation and jobs, protect Social Security and Medicare, institute sane policies on guns and violence, and curb the pollution that is causing global warming."
He had a basic campaign website and online fundraising apparatus posted as of Thursday afternoon.
- CNN Political Editor Paul Steinhauser contributed to this report