When Candidate Trump first referred to “the swamp,” he was talking about the bog of Beltway lobbyists and “establishment” politicians. But President Trump’s first year in office has revealed that the real swamp is the unchecked power of those who actually run Washington: the two million members of the federal bureaucracy. That civil-servant corps was turbocharged by the Obama administration’s rule-making binge, and it now has more power—and more media enablers—than ever. We live in an administrative state, run by a left-leaning, self-interested governing class that is actively hostile to any president with a deregulatory or reform agenda.

It’s Lois Lerner, the IRS official who used her powers to silence conservative nonprofits. It’s the “anonymous” officials who leak national-security secrets daily. It’s the General Services Administration officials who turned over Trump transition emails to Special Counsel Robert Mueller in the absence of a warrant. It’s the Consumer Financial Protection Bureau’s Leandra English, who tried to stage an agency coup. It’s the EPA’s “Scientific Integrity Official” who has taken it upon herself to investigate whether Scott Pruitt is fit to serve in the office to which he was duly appointed. It’s the thousands of staffers across the federal government who continue to pump out reports on global warming and banking regulations that undermine administration policy.

More broadly, it is a federal workforce whose pay and benefits are completely out of whack with the private sector. A 2011 American Enterprise Institute study found federal employees receive wages 14% higher than what similar workers in the private sector earn. Factor in benefits and the compensation premium leaps to 61%. Nice, huh?

These huge payouts are the result of automatic increases, bonuses, seniority rules and gold-plated pensions that are all but extinct in the private sector. The federal workforce is also shielded by rules that make it practically impossible to fire or discipline bad employees, to relocate talent, or to reassign duties. These protections embolden bureaucrats to violate rules. Why was Ms. Lerner allowed to retire with full benefits? Because denying them would have cost far more—and required years of effort.

It’s been nearly 40 years since the last civil-service overhaul. Trump appointees are doing valiant work to shift the bureaucracy by canceling programs and using buyouts to cut staff. White House Counsel Don McGahn —a veteran at battling the federal career elite—is recruiting a generation of judicial nominees who are experts in administrative law. And Mick Mulvaney, director of the Office of Management and Budget, tapped another administrative-law genius, Neomi Rao, to head the deregulatory effort.

Even so, Trump officials spend most of their days fighting rearguard actions against their own employees when they should be implementing the president’s broad vision across the executive branch. Since congressional Republicans refuse to slash agencies, the least they can do is make oversight a priority.

Americans generally have a higher opinion of federal agencies than they do of Congress, though the Veterans Affairs and Justice departments have seen their ratings slip in recent years, as has the Environmental Protection Agency. But government overhaul is an issue that unites across parties on grounds of accountability, fairness and spending. Ask Wisconsin Gov. Scott Walker.

Civil-service reform’s bipartisan appeal means it has a shot in the Senate. The Chuck Schumers and Elizabeth Warrens will fight for their federal union buddies. But will Democrats like Jon Tester, Claire McCaskill, Joe Manchin and Joe Donnelly —who represent conservative or right-to-work states—go to bat for the likes of Lois Lerner? Will they defend the CFPB, the majority of whose employees take home six-figure salaries, when the median personal income in the U.S. is about $31,000?

If Democrats insist on engaging in class warfare, Republicans should take on the governing class. Washington is now home to a bureaucratic elite, fantastically paid and protected, divorced from economic reality, and self-invested in thwarting conservative policy efforts. Let’s drain the swamp, or at least make it smaller.

Write to kim@wsj.com.