The Senate Foreign Relations Committee unanimously approved Sen. John KerryJohn KerryWith help from US, transformative change in Iran is within reach Ellison comments on Obama criticized as 'a stupid thing to say' 'Can you hear me now?' Trump team voices credible threat of force MORE (D-Mass.) to be the next secretary of State earlier on Tuesday, setting up a vote on the Senate floor later in the day. Kerry's nomination later passed the Senate with overwhelming support.

Kerry, the former chairman of the committee, received a voice vote from his colleagues. His nomination had been expected to sail through after Republicans urged President Obama to nominate him instead of Ambassador to the United Nations Susan Rice, after her role in the administration's reaction to the Benghazi attacks last year. 

Patrick will announce his appointment to Kerry's seat on Wednesday. Patrick's former chief of staff, William “Mo” Cowan, and Victoria ­Kennedy, widow of Sen. Edward Kennedy (D-Mass.), are considered frontrunners for the pick. 

Patrick has set the special election primary date for April 30, and the general election for June 25.

Though Rep. Stephen Lynch (D-Mass.) insists he has not yet made up his mind about a run, sources say he is likely to jump into the race soon after Kerry steps down, setting Democrats up for an unwanted primary race. Lynch's flirtation with campaign highlights vulnerabilities some Democrats see in Rep. Edward MarkeyEd MarkeyDem senators ask Bannon for more info about Breitbart contact Dem lawmaker: FCC now stands for 'Forgetting Choice and Competition' Senate Dems want Trump to release ethics waivers, visitor logs MORE (D), the front-runner to win the Democratic nomination to succeed Kerry

No Republican has yet officially announced his or her intentions to run for the seat, but Republicans in Massachusetts expect Scott Brown (R) to run again, just a few months after he lost to Sen. Elizabeth WarrenElizabeth WarrenChris Christie gives Trump a 'B' on presidency so far Warren gives Trump's first 100 days an 'F' Overnight Finance: Tariffs on Canadian softwood lumber | Trump eyes 15 percent corporate tax rate | Border wall funding fight | Deal on vote for trade pick MORE (D-Mass.)

Secretary of State Hillary ClintonHillary Rodham ClintonObama to net 0K for Wall Street speech: report O'Reilly: Fans will be 'shaken' when truth comes out about Fox exit Overnight Cybersecurity: White House adviser ditches cyber panel over 'fake news' | Trump cyber order 'close' | GOP senator pushes for clean renewal of foreign intel law MORE has said her last day on the job will be Friday.

--This post was updated at 5:04 p.m.

Alexandra Jaffe contributed.