The steady pace of Biden’s announcements frustrates some progressives in his party.

Many in the left wing of the Democratic Party want President-elect Joseph R. Biden Jr. to move faster in announcing substantive plans for his administration, such as a sweeping plan to bring the coronavirus crisis under control, urging him to provide more than just glimpses of what he might do early on.

At the same time, many Republicans have refused to accept Mr. Biden as the winner of the election, something Senate Majority Leader Mitch McConnell only acknowledged just a day ago. He urged other Republicans to do the same.

But despite the tensions with opposite ends of the political spectrum, Mr. Biden has maintained a steady and deliberate pace in developing a unified platform with his advisers. He has revealed plans for his administration, introducing his cabinet picks, over weeks, not days — most recently selecting Pete Buttigieg, the former mayor of South Bend, Ind., to lead the Transportation Department. In the coming days, he is expected to choose Jennifer M. Granholm, a former governor of Michigan, to serve as energy secretary and Gina McCarthy, a former administrator of the Environmental Protection Agency, to be his senior adviser on climate change.

Mr. McConnell’s public recognition of Mr. Biden’s win and belated congratulations inspired some optimism among Democrats that the relative monotony of recent weeks, during which President Trump has waged a daily campaign challenging the election results across multiple states, might at last be breaking.

And while Mr. Biden’s slow rollout of his plans for the next four years has helped pre-empt an outcry from factions in the Democratic Party that are vying for influence, it has also increasingly fueled frustrations from interest groups and the party’s progressive wing, both of which said they had felt neglected in the coalition that helped bring him to power.