OXON HILL, Md. — Donald J. Trump was still a New York businessman when he was booed at the Conservative Political Action Conference in 2015 after he proposed fighting ISIS with troops on the ground in the Middle East.

Flash forward five years, and there was no room at the annual conservative conference this week for booing of anything related to President Trump, including the procession of his adult children and their spouses who appeared here on Friday to bash socialism and make the case for his re-election.

CPAC has been transformed from a gathering of libertarians where establishment Republicans mingled with fringe conservative activists into a stage for Mr. Trump and his top advisers and allies to road-test winning messages for the campaign trail. Republicans not on board with defending the president and his agenda, like Senator Mitt Romney of Utah, were disinvited from the conference this year.

“We need a CPAC full of happy warriors ready to deploy across the country!” Senator Marsha Blackburn of Tennessee announced from the stage on Thursday, reminding the audience to “make certain we have four more years of President Donald Trump!”