Jim Conroy, the wily and witty senior adviser to Governor Charlie Baker, who managed the Republican’s successful 2014 campaign, is leaving state government service to return to political and public affairs consulting.

The 35-year-old Watertown resident, who served as Baker’s top political adviser and effectively his number-two staffer in the executive branch, will continue to informally advise the governor on political issues.

He will also “work on initiatives in Massachusetts that are supportive of the governor’s agenda,’’ Conroy said — naming the push to raise the cap on charter schools as an example — and help advise the state Republican Party.

Tim Buckley, Baker’s communications director, is being promoted to senior adviser, while maintaining his communications title and portfolio.

In his new role, Buckley said, he will assist the governor, Lieutenant Governor Karyn Polito, and Baker’s chief of staff, Steve Kadish, in carrying out the administration’s agenda, meeting with outside groups, and working with Cabinet secretaries and agencies.

Buckley, a 32-year-old Medfield native and South Boston resident, said that after growing up in Massachusetts, the opportunity “to work for the people of Massachusetts and the governor and lieutenant governor, who know so much about how state government works, and care so much about the Commonwealth, it is just a huge honor.’’

Buckley, who served as communications director on Baker’s 2014 campaign and is a graduate of Colorado College, said Conroy leaves “huge shoes to fill,’’ and he’s excited for the new challenge and “to take on a little bit more responsibility.’’

Conroy’s last day was Monday, the same day Buckley’s promotion took effect.

The departure of Conroy, who is quick with a joke and is known among his colleagues for his savvy political sense, was widely expected. Originally, he had planned to stay in state government for only a few months after steering a Republican to a gubernatorial victory in a Democratic state.

Still, the move marks the first change in Baker’s tight inner circle of senior staffers since he was sworn in as governor on Jan. 8, 2015.

Insiders see Conroy as likely to play a large role in Baker’s expected 2018 reelection effort. The governor has not yet said whether he will run for a second term.

Outside government, Conroy said he will eventually take on corporate clients and may work with other political candidates — New England Republicans, in particular.

Conroy, who attended Syracuse University, previously served as the campaign manager for a Senate candidate in Pennsylvania, executive director of the Connecticut Republican Party, and manager of a gubernatorial bid in Connecticut, and he worked for the Republican National Committee.

Baker said he came to respect Conroy’s leadership, judgment, and common sense over the course of the gubernatorial race. The governor added that he views his aide as a friend and “as somebody whose advice and whose instinct and whose insight on public policy matters, and on governing generally, are first rate.’’

In another change in staffing, the Baker administration has hired Tom Dickens as director of external affairs.

Dickens, a former top official in New Jersey Governor Chris Christie’s 2016 presidential and 2013 gubernatorial campaigns, will be a key administration liaison with outside groups, from the Massachusetts Municipal Association, which represents cities and towns, to providers of opioid addiction treatment.

Joshua Miller can be reached at joshua.miller@globe.com. Fol-low him on Twitter @jm_bos and subscribe to his weekday e-mail update at bostonglobe-.com/politicalhappyhour.