A prominent Democrat in Governor Charlie Baker’s administration will leave to take a job with a downtown lobbying firm, Baker aides said Thursday.

Carlo Basile, who joined the executive branch as chief secretary after serving as an East Boston state representative, will join the firm of Smith, Costello & Crawford in January, officials said.

Personally close to Baker, Basile was a political ally during the 2014 election and has helped ease relations between the GOP administration and the Democrat-controlled Legislature.

In a statement, Basile said he looks “forward to spending more time with my two boys and pursuing a new career opportunity.’’

Basile’s responsibilities will be downtown spread among three other Baker aides. Senior adviser Tim Buckley will retain his title and add that of chief secretary. Baker legislative director Ryan Coleman will take the newly created position of deputy chief secretary.

Kaitlyn Sprague, a State House veteran, will move into Coleman’s post as legislative director and serve as the administration’s main contact for lawmakers.

The changes are effective the first of the year.

Basile’s departure comes as Baker suffered some setbacks on Election Day, watching the pro-charter-school initiative he campaigned for go down in defeat, while the legalization of marijuana, a measure he opposed, passed.

“Carlo has been a big part of our administration’s success when it comes to crossing party lines and working with the Legislature to achieve our agenda and I hate to see him go, but family comes first,’’ Baker said in an e-mailed statement.

Basile was one of an early wave of Baker appointees, his appointment coming within weeks of Baker’s narrow 2014 victory over Democrat Martha Coakley, who was then the attorney general.

With the appointment, Baker revived an office that existed in previous Republican administrations, a post often linked with patronage. In his role, Basile oversaw appointments to various state boards and commissions.

Basile’s hiring was not the first time he crossed party lines. In 2006, a year before winning his House seat, he irked Democrats by endorsing the GOP gubernatorial nominee, Kerry Healey.

The State House has seen a steady parade into the influence-peddling industry. Another early Baker hire, former campaign manager James Conroy, left the administration earlier this year and has his own consulting practice.

Lawmakers have also beaten a well-worn path to lobbying firms, including former Democratic state representative Michael Costello, who resigned in 2014 to join the firm where Basile is headed. The firm’s founder, James Smith, is also a former state representative.

Jim O’Sullivan can be reached at jim.osullivan@globe.com. Follow him on Twitter at @JOSreports.