And in truth, though Americans’ faith in Congress is minute, most do not even know how bad the Senate has become. Without time to watch C-SPAN, few are aware that the world’s supposedly greatest deliberative body has spent most of its time of late churning through confirmations of midlevel executive branch officials and federal judges. Those nominations — once routinely approved unanimously — now take days and must be considered one at a time.

Robert Dallek, a historian and biographer of Lyndon B. Johnson, said such sclerosis had ebbed and flowed in the past. Harry S. Truman routinely railed against the “good-for-nothing, do-nothing Congress” that failed to pass legislation to establish federal health insurance, protect civil rights or even stop the lynching of Black Americans in the South.

But, Mr. Dallek added, the nation feels like a tinderbox right now.

“They are putting democracy in danger because the frustration that comes can lead to civil strife,” Mr. Dallek said. “The nation is terribly divided at the moment.”