Hochul is expected to make the announcement Thursday, according to the source.
The selection comes as Hochul continues to build out her governing office.
CNN previously reported that in the coming days Hochul would tap her replacement. That partner, Hochul has indicated, will come from New York City, where she is working overtime to build out a base of support and introduce herself to voters.
Benjamin, a Democrat, represents District 30, which includes his birthplace Harlem and the Upper West Side. He is senior assistant majority leader and chairman of the budget and revenue committee in the state Senate.
He ran an unsuccessful bid for New York City comptroller earlier this year.
Benjamin, 44, is known for criminal justice reform and affordable housing efforts. He sponsored legislation signed into law last June that outlawed chokeholds by police officers.
Benjamin was among the Democrats who called for then-Gov. Andrew Cuomo to resign in March after allegations of sexual harassment grew and reiterated those calls after New York Attorney General Letitia James’ report on the allegations was released earlier this month.
“The @NewYorkStateAG’s report makes it clear that Governor Cuomo must resign for the good of New York,” he tweeted earlier this month and thanked the women who came forward.
State Sen. Jamaal Bailey, another New York City-based lawmaker reportedly on the short list for the number two position, congratulated Benjamin on Twitter Wednesday.
Bailey wrote: “All about the Benjamins about to be played on a statewide level! As we reimagine New York, we continue to move forward with the best. Huge congrats to my brother @NYSenBenjamin and his wonderful family on this well-deserved appointment as our new Lieutenant Governor! #HarlemWorld”
Benjamin worked in investment banking for Morgan Stanley before jumping full-time into politics and was a member of Former President Obama’s National Finance Committee, according to his website.
CNN reached out to Benjamin and Hochul’s office for comment.