An informal coalition of influential conservative leaders and groups, some with close connections to the White House, has been quietly working to nurture protests and apply political and legal pressure to overturn state and local orders intended to stop the spread of the coronavirus.

An American lobbyist on Friday admitted brokering access to President Trump’s inauguration for a pro-Russian Ukrainian oligarch in a scheme that highlighted the rush by foreign interests to influence the new administration.

For Elliott Broidy, Donald J. Trump’s presidential campaign represented an unparalleled political and business opportunity. An investor and defense contractor, Mr. Broidy became a top fund-raiser for Mr. Trump’s campaign when most elite Republican donors were keeping their distance, and Mr. Trump in turn overlooked the lingering whiff of scandal from Mr. Broidy’s 2009 guilty plea in a pension fund bribery case.