Rep. Joe Kennedy Joseph (Joe) Patrick KennedyDemocrats see fundraising spike following Ginsburg death Massachusetts town clerk resigns after delays to primary vote count Bogeymen of the far left deserve a place in any Biden administration MORE III (D-Mass.) will formally launch a primary challenge to Sen. Ed Markey Edward (Ed) John MarkeyA game theorist's advice to President Trump on filling the Supreme Court seat Watchdog confirms State Dept. canceled award for journalist who criticized Trump 3 reasons why Biden is misreading the politics of court packing MORE (D-Mass.) on Saturday, a source confirmed to The Hill on Wednesday.

The impending announcement had first been reported by The Boston Globe, which cited two sources close to Kennedy saying he would make his announcement at a breakfast with supporters and local community members.

Kennedy has already notified Markey of the primary challenge, one person told the Globe.

ADVERTISEMENT

Kennedy, 38, has been floated as a potential Senate candidate in recent weeks, setting up an intraparty generational clash with Markey, 73, a former longtime House member who is seeking a second term in the Senate after first assuming his seat in 2013.

The sitting senator's campaign has been boosted by endorsements from progressive lawmakers, including Rep. Alexandria Ocasio-Cortez Alexandria Ocasio-CortezOn The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline McCarthy says there will be a peaceful transition if Biden wins Anxious Democrats amp up pressure for vote on COVID-19 aid MORE (D-N.Y.), with whom he has worked closely on the Green New Deal, progressives' proposal to combat climate change.

"Ed Markey is a proud and strong progressive champion for working families, not just in Massachusetts but across the country. And his leadership in authoring the Green New Deal, along with me, and carrying it in the United States Senate is emblematic of the kind of work that he does for working families across the country," Ocasio-Cortez said in a video endorsement.

Meanwhile, Kennedy — the grandson of Robert F. Kennedy – has been encouraged to run by Sen. Kyrsten Sinema (D-Ariz.).

A recent survey from Suffolk University and The Boston Globe found Kennedy leading Markey by double digits in a theoretical head-to-head match-up.