IT’S NO SURPRISE that Senate Republicans grouse about Obama administration policies on enforcing civil rights laws or limiting greenhouse-gas emissions. They are entitled to their policy views.

It’s a different matter for Republican leaders to manifest their views by blocking confirmation to Cabinet positions of the officials in charge of those policies. By doing so, on absurdly flimsy pretexts, Republicans not only impede the president’s nominations for labor secretary and chief of the Environmental Protection Agency (EPA), but also undermine the normal flow of government, upon which presidents of both parties have depended. They help to subvert whatever is left of Americans’ faith in government. And they may give frustrated Democrats an excuse to rewrite Senate rules in a way that both parties will have cause to regret.

Last Thursday, Republicans boycotted the Senate Environment and Public Works Committee, thereby preventing a vote on the nomination of Gina McCarthy to lead the EPA. Ms. McCarthy, who was easily confirmed by the Senate to her current position as chief of the EPA’s clean air division, previously served as a top state environmental official under Republican governors in both Connecticut and Massachusetts. Competent and well qualified, she’s an obvious choice to lead the agency.

Still, Republicans unhappy about the administration’s policies to limit greenhouse-gas emissions and other pollutants — “job-killing regulations,” in GOP parlance — demanded she submit answers to more than 1,000 questions, then deemed her answers inadequate. The deluge may be a record for a Cabinet appointee; more than 650 were submitted just by Sen. David Vitter (R-La.).

The Republican playbook is only slightly different in the case of Thomas Perez, chief of the Justice Department’s civil rights division, who is the nominee to become labor secretary. Democrats highly regard Mr. Perez, a former secretary of labor in Maryland, for his aggressive action on voting rights, police abuse and fair lending cases. Republicans dislike him for the same record. Again, there is no question that he is qualified for the job. But Mr. Perez, who if confirmed would be the only Hispanic in the Cabinet, has been the target of baseless personal attacks, with Sen. John Cornyn of Texas questioning Mr. Perez’s “temperament” and “competence.” It is Washington at its worst, and that’s saying something.

At a Senate hearing last week, Republicans affected indignation — and strained credulity — by insisting that Mr. Perez had failed to stick up for a federal contracting program designed mainly to benefit minority and low-income workers. It was novel to hear GOP lawmakers posing as champions of the disadvantaged, but their protests were nothing but a pretext.

Americans elected Barack Obama president, and reelected him. He’s entitled to his Cabinet. It’s possible that Republicans will muster the 41 votes needed in the Senate to block both nominations — despite their strong qualifications and high ethical standards. If they do, Americans will be under no illusions that the GOP has led Washington to new lows of dysfunction.