WASHINGTON — Donald J. Trump came to Pennsylvania Avenue on Monday and offered a freewheeling, circuslike glimpse of what the nation’s capital might look like if he is successful in his quest to occupy that big, white house on the 1600 block of the street.

Mr. Trump’s whirlwind day in Washington — part of his effort to demonstrate that he is running a serious presidential campaign — took him from an imposing law firm to a news conference at a hotel he is building here to a much-anticipated policy speech before a pro-Israel group, all with the Manhattan businessman’s characteristic mix of panache, policy and showmanship.

His first stop was at The Washington Post, for an editorial board meeting where he unveiled five members of his foreign policy team: Keith Kellogg, Carter Page, George Papadopoulos, Walid Phares and Joseph E. Schmitz. Though Mr. Trump has been promising for months to release the names of his foreign policy advisers, those he presented on Monday have come under fire in the past. But the team will be led by Jeff Sessions, a member of the Senate Armed Services Committee.