Maryland Lt. Gov. Samuel W. Bogley said today that he is "leaning" toward accepting State Sen. Harry J. McGuirk's offer to become his running mate in the Baltimore legislator's challenge to Gov. Harry Hughes in the Democratic primary.

Even while Bogley sat in his office pondering whether to join the underdog McGuirk ticket, pressure was mounting on Speaker of the House Benjamin L. Cardin to reverse himself and agree to replace Bogley on the Hughes ticket.

There were these other developments in the gubernatorial derby:

* Bogley, who is being encouraged by his family to grab an opportunity to run against Hughes, said he thought he would probably join the McGuirk ticket but reserved a final decision until after Hughes announces his running mate.

* Cardin, who joined Hughes on the governor's yacht over the Memorial Day weekend, refused to deny that he and Hughes discussed his joining the ticket. "No offer has been made to me and I have not sought the job," he said. Sources said Hughes wanted Cardin to guarantee he would accept the post if it were offered and that Cardin wanted a guarantee about his role in the administration.

* Hughes staffers insisted that the question of a running mate is still open. Many in the staff would prefer Cardin but First Lady Patricia Hughes, who is a major factor in the selection, prefers the front-runner, Baltimore state Sen. J. Joseph Curran.

* One Hughes staffer said an announcement might come Wednesday. Another said it would be no earlier than next week.