WASHINGTON — Two more senior aides to President Trump announced on Tuesday that they were stepping down, the latest staff changes in a White House operation that has been whipsawed over the last two and a half years by the most turnover of any in modern times.

Johnny DeStefano, a counselor to the president, and Shahira Knight, the White House legislative affairs director, separately disclosed they would leave for new opportunities. Neither departure was a surprise, but they deprive Mr. Trump of two top lieutenants as he heads toward his re-election campaign.

Mr. DeStefano has been a key member of Mr. Trump’s circle since he took office, earning the president’s trust as he was handed more and more responsibility. By the end, Mr. DeStefano was in charge of the Offices of Presidential Personnel, Intergovernmental Affairs, Political Affairs and Public Liaison.

Ms. Knight took over as legislative director only 10 months ago, making her the president’s official envoy to Congress. But with gridlock already gripping Capitol Hill and the 2020 campaign likely to aggravate partisan divisions, she chose to leave as the prospects of major legislation dimmed.