KIMBERLEY STRASSEL: Devin Nunes, Washington’s Public Enemy No. 1: What did the FBI do in the 2016 campaign? The head of the House inquiry on what he has found—and questions still unanswered.

It’s 105 degrees as I stand with Rep. Devin Nunes on his family’s dairy farm. Mr. Nunes has been feeling even more heat in Washington, where as chairman of the House Select Committee on Intelligence he has labored to unearth the truth about the Federal Bureau of Investigation’s activities during and after the 2016 presidential campaign. Thanks in large part to his work, we now know that the FBI used informants against Donald Trump’s campaign, that it obtained surveillance warrants based on opposition research conducted for Hillary Clinton’s campaign, and that after the election Obama administration officials “unmasked” and monitored the incoming team.

Mr. Nunes’s efforts have provoked extraordinary partisan and institutional fury in Washington—across the aisle, in the FBI and other law-enforcement and intelligence agencies, in the media. “On any given day there are dozens of attacks, each one wilder in its claims,” he says. Why does he keep at it? “First of all, because it’s my job. This is a basic congressional investigation, and we follow the facts,” he says. The “bigger picture,” he adds, is that in “a lot of the bad and problematic countries” that Intelligence Committee members investigate, “this is what they do there. There is a political party that controls the intelligence agencies, controls the media, all to ensure that party stays in power. If we get to that here, we no longer have a functioning republic. We can’t let that happen.” . . .

It got worse. This spring Mr. Nunes obtained information showing the FBI had used informants to gather intelligence on the Trump camp. The Justice Department is still playing hide-and-seek with documents. “We still don’t know how many informants were run before July 31, 2016”—the official open of the counterintelligence investigation—“and how much they were paid. That’s the big outstanding question,” he says. Mr. Nunes adds that the department and the FBI haven’t done anything about the unmaskings or taken action against the Flynn leakers—because, in his view, “they are too busy working with Democrats to cover all this up.”

He and his committee colleagues in June sent a letter asking Mr. Trump to declassify at least 20 pages of the FISA application. Mr. Nunes says they are critical: “If people think using the Clinton dirt to get a FISA is bad, what else that’s in that application is even worse.”

Mr. Nunes has harsh words for his adversaries. How, he asks, can his committee’s Democrats, who spent years “worrying about privacy and civil liberties,” be so blasé about unmaskings, surveillance of U.S. citizens, and intelligence leaks? On the FBI: “I’m not the one that used an unverified dossier to get a FISA warrant,” Mr. Nunes says. “I’m not the one who obstructed a congressional investigation. I’m not the one who lied and said Republicans paid for the dossier. I’m just one of a few people in a position to get to the bottom of it.” And on the press: “Today’s media is corrupt. It’s chosen a side. But it’s also making itself irrelevant. The sooner Republicans understand that, the better.”

His big worry is that Republicans are running out of time before the midterm elections, yet there are dozens of witnesses still to interview. “But this was always the DOJ/FBI plan,” he says. “They are slow-rolling, because they are wishing and betting the Republicans lose the House.”

I wonder what else they’re doing besides “wishing and betting?”