WASHINGTON — Paul Ryan, the House speaker, is by all accounts a man of integrity and intelligence. When it came to the failed attempt by House Republicans to scrap President Obama’s legacy health care law and replace it with something that better reflected their conservative values, Mr. Ryan did as well as could be expected given the sharp divisions within his party’s ranks. But it may be time for him to quit his post as speaker. It is a position for which, thus far, he has proved remarkably unsuited and in which he has allowed the House to suffer a series of humiliations.

As its central feature, the Constitution mandates a deliberate separation between the legislative and administrative, or executive, branches of government. This is not a matter of architecture, a quirk of structural whim. The separation is intended to ensure that no single person or branch of government will amass an excess of power and that the citizenry will retain a firm grip on the government’s policy-making process. If the Congress cedes its independence, the entire constitutional framework, which depends on a system of checks and balances, is compromised.

Maintaining that carefully constructed system is a particular duty of the speaker. Mr. Ryan, though pledged to uphold the Constitution, has taken to acting as though he and the Republicans he leads are members of the White House staff.

Under Mr. Ryan’s leadership, the chairman of the House Intelligence Committee, in the midst of conducting hearings looking into possible wrongdoing by the president or his advisers, briefed the president on the progress and findings of the investigation. The chairman, Devin Nunes, facing ethics complaints over his conduct, has temporarily stepped down, with Mr. Ryan’s approval. But the speaker was under an obligation to have immediately removed Mr. Nunes from his chairmanship in order to assert the House’s independence from the White House. Instead, for days — because he, too, apparently sees himself as one of Donald Trump’s assistants — Mr. Ryan continued to back Mr. Nunes.