President Trump announced on Tuesday that he would nominate Mike Pompeo, the director of the C.I.A., to be the next secretary of state now that Rex Tillerson has been pushed out. This is bad news for the country and the world.

If confirmed, Mr. Pompeo will bring to the job not the discretion and objectivity of a former intelligence chief, but instead the habits of a fierce ideologue, which is precisely what he continued to be as C.I.A. director, typically a nonpartisan position. He has been the most political head of the agency since William Casey in the 1980s. Mr. Pompeo has repeatedly stepped out of the proper role of an intelligence director to be an advocate for hawkish policies. The ruthless partisanship he displayed as a congressman foreshadows how he will perform at the State Department.

Mr. Pompeo is a staunch defender of Mr. Trump and echoes his preferences on major national security and foreign policy matters. That’s likely the main reason he was given Mr. Tillerson’s job as the United States’ top diplomat. As secretary of state, Mr. Pompeo would reinforce Mr. Trump’s more destructive inclinations on several key issues:

Iran. In commenting to reporters on the appointment, Mr. Trump singled out the Iran nuclear agreement as an issue on which he disagreed with Mr. Tillerson, saying, “I think it’s terrible; I guess he thought it was O.K.” But with Mr. Pompeo, continued the president, “we have a very similar thought process.”

Mr. Pompeo has indeed been a fervent foe of the 2015 nuclear agreement. While in Congress, he pursued every possible avenue to discredit and undermine it. He talked of imaginary “secret side deals” that the Obama administration had allegedly made with Iran and has played down the costs of bombing Iran. As director of the C.I.A., Mr. Pompeo has likened Iran to the Islamic State and has tried to make a case that Iran is allied with Al Qaeda, even ordering another dive into already-exploited documents captured in the raid that killed Osama bin Laden, and then taking the highly irregular step of furnishing a cherry-picked result to an advocacy group that opposes the nuclear agreement.