The Senate Foreign Relations Committee unanimously approved Sen. John KerryJohn Forbes KerryBringing the American election experience to Democratic Republic of the Congo Some Dems sizzle, others see their stock fall on road to 2020 The Hill's 12:30 Report 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 MarkeyEdward (Ed) John MarkeyOvernight Regulation: FTC launches probe into Equifax | Dems propose tougher data security rules | NYC aims to slash greenhouse gas emissions | EPA to reconsider Obama coal ash rule Overnight Cybersecurity: Kaspersky to testify before House | US sanctions Iranians over cyberattacks | Equifax reveals flaw that led to hack Dems propose data security bill after Equifax hack 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 Ann WarrenSenate Dems hold floor talk-a-thon against latest ObamaCare repeal bill Trump bets base will stick with him on immigration Dems call for action against Cassidy-Graham ObamaCare repeal MORE (D-Mass.)

Secretary of State Hillary ClintonHillary Diane Rodham ClintonBiden slams Trump over golf gif hitting Clinton Overnight Cybersecurity: Equifax hit by earlier hack | What to know about Kaspersky controversy | Officials review EU-US privacy pact Overnight Tech: Equifax hit by earlier undisclosed hack | Facebook takes heat over Russian ads | Alt-right Twitter rival may lose domain MORE has said her last day on the job will be Friday.

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

Alexandra Jaffe contributed.