It’s the paradox that, perhaps, best sums up this perplexing political era: At a time when the American public is famously divided, American government is dominated by one party.

Since the 2016 elections, Republicans have simultaneously held the White House, control of the House of Representatives and the Senate, most governorships and majorities in most state legislatures, and a friendly majority of U.S. Supreme Court justices.

This is the case even though Democrats won more total votes in the latest elections for president and the two houses of Congress, even though Gallup’s monthly poll on party affiliations shows Democrats clinging to a slim lead over Republicans, and even though Republican Donald Trump’s approval poll numbers have been underwater almost since he entered the Oval Office.

It’s a phenomenon that frames the November elections for congressional and many state offices across the country, as well as Republicans’ efforts to solidify conservatives’ advantage on the Supreme Court by winning Senate confirmation for the nominee Trump plans to introduce Monday to replace retiring Justice Anthony Kennedy.

It’s a situation that has liberals screaming, with New York magazine columnist Jonathan Chait decrying “minority rule” and New York Times columnist Michelle Goldberg saying it threatens the U.S. political system with a “legitimacy crisis.”

It’s a frustration that boils especially hot in California, whose large liberal base is a big reason for whatever pluralities Democrats can claim in nationwide voting and polling numbers.

“Obviously, that’s why they worked so hard to gerrymander the states,” California Democratic Party Chairman Eric Bauman cracked when the subject of Republicans’ grip on power was broached.

How it happened

Political scientists credit several factors for Republicans having the White House and edges over Democrats of 236-193 in the House, 51-47 in the Senate, 33-16 among governors and 32-13 among state legislatures, topped off by five Supreme Court justices appointed by Republican presidents against four by Democrats.

• The American system is built to rein in majorities. Currently, mostly Republican states draw disproportionate per-capita power from the Electoral College of choosing presidents and the two-per-state set-up of the Senate. The GOP’s control of statehouses allows the party to draw favorable House district lines in many states. There’s little reward for Democrats from piling up huge vote margins in House balloting in overwhelmingly blue metropolitan areas such as Los Angeles. To win a majority of seats in the House, it is believed Democrats must win the combined vote nationwide by at least 5 percentage points.

“This is the system we’ve got, and Democrats have to find a way to win despite it,” said Jack Pitney, professor of politics at Claremont McKenna College and a former Republican National Committee research director.

• Barack Obama’s eight-year presidency actually backfired on Democrats because of bad timing. In 2010, the usual midterm election backlash against the president’s party reinforced Republicans’ control of state governments, putting the GOP in charge of key redistricting based on the decennial census.

This has created “probably a dozen or a dozen and a half additional seats for Republicans in the House because of partisan gerrymandering,” said Thomas E. Mann, resident scholar at the Institute of Government Studies at UC Berkeley and senior Fellow in Governance Studies at the Brookings Institution.

• Trump has made the most of the 46.1 percent of Americans who voted for him (vs. 48.2 percent for Democrat Hillary Clinton) and roughly 43 percent of Americans who view him favorably now (according to the Real Clear Politics average of major polls on Friday, July 6).

“Our system is not one of majority rule but one of minority rule with majority acquiescence,” said Dan Schnur, a professor at USC’s Annenberg Center and a former long-time Republican spokesman and strategist. “If you have a smaller group of voters who care passionately, and I have a larger group that’s not that motivated, you’re probably going to beat me.”

Schnur said that Trump, in refusing to try to expand his voter base, has “decided that he’s willing to trade quantity of support for fervency of support. … The most relevant question in this (November’s) election is whether he’ll be more effective at motivating his supporters or his opponents.”

What now?

This is not the first time that one party scored a political pick-six: presidency, House, Senate, governorships, legislatures and Supreme Court. Democrats did it most recently after the Lyndon Johnson landslide of 1964. Republicans did it in George W. Bush’s first term, in the rally-round-the-flag moment after the Sept. 11, 2011 terrorist attacks.

What’s different is that in those cases, one party’s dominance reflected an actual advantage in nationwide voting patterns and public opinion polling, serving the apparent will of the people as you’d expect from representative government.

Democrats might take heart from the rest of that history. In each case, the out-of-power party quickly bounced back. Johnson’s re-election bid fell apart, Republican Richard Nixon was elected president in 1968, and his appointments began an era of conservative majorities in the Supreme Court that continues today. Bush vowed to use the “political capital” he said he’d earned in his 2004 re-election, but “decided to use it in ways people didn’t want,” Pitney said; Democrats won back Congress in 2006 and Obama was elected in 2008.

“There have been many times in history when one party seemed to have a lock on government,” Pitney said. “But events have a way of picking the lock.”

“American voters are natural course-correctors,” Schnur said. “They’re always looking to rein in whichever side is going too far.”

That happens when a party flush with power tries to make changes the public isn’t asking for. That happened to Bush, Pitney said, in his failed push to partially privatize Social Security. It could be happening to Trump and other Republican leaders now, Mann said, with immigration policy and tax cuts for corporations and high earners, and resistance to popular calls for more gun control.

Republicans’ reign might yet survive the Nov. 6 elections if the economy remains strong, or if Democrats overreach, too, Pitney said. Proposing to abolish the Immigration and Customs Enforcement agency, as some Democrats are doing, could be such a mistake, he said.

Democrats need to pick up at least 23 Republican seats to win control of the House; they could flip as many as five of those in L.A. and Orange counties. Democrats winning control of the Senate is considered less likely.

Bauman, the state Democratic chairman, said his party’s recovery has already begun with encouraging results in the June 5 state primary and elsewhere.

“The only way to overcome this,” Bauman said of Republicans’ current advantage in electoral math, “is for people to get out and vote.”

“You certainly understand their frustration,” Schnur said of Democrats. “But both sides agree on the rules before the campaign starts.”