Fly over Eastern Washington’s 5th Congressional District and you might need a geologist’s eye to sense the fire and ice that marked this land of picturesque small towns and gently rolling fields.

Jutting out from those gentle hills, towers of jagged basalt bear witness to eruptions past. Deep, cliff-shaded coulees mark the gouging path of ancient ice-age floods.

And in the realm of politics, the 5th District led a 1994 upheaval that helped transform the United States into the Divided States.

In 1994, voters in the district voters booted out the Speaker of the House.

Nationwide, Republicans that year seized a majority in both houses of Congress for the first time since the 1950s. A now-familiar map of red states spread from the South up through the country’s midsection. The health insurance industry’s “Harry and Louise” ads crushed President Bill Clinton’s effort to reform health care. Republican leader and future House Speaker Newt Gingrich pushed a “Contract with America.” Christian conservatives flocked to the polls. Talk radio emerged as a force, raining rhetorical lava on liberals, Democrats and big government.

Voters showed the door to a generation of longtime legislators.

Most prominent among them was House Speaker Tom Foley, a Democrat, who for 30 years had represented the 5th District with bipartisan effectiveness, bringing home transforming benefits of federal power and money: farm subsidies, economic development, highway construction, social programs, environmental cleanup, higher education, military appropriations and the cultivation of foreign trade.

Even though Foley won in urban Spokane, he lost the election in the hinterlands — the same pattern now evident in the nation’s urban-rural divide.

Pundits were astonished. It was the first time since the Civil War that a speaker had lost his seat.

What were the voters thinking?

More important, what are they thinking now?

Today, in a national campaign season that calls to mind the scorched-earth year when Foley fell, pollsters by the hundreds are trying to figure out what the voters might do.

But the 5th, once the scene of that political Mount St. Helens, has turned into flyover country. It leans Republican. Its representatives to Olympia, as well as Washington, D.C., want less government.

Their message: Butt out, bureaucrats. Get lost, big government.

When Foley was ousted, his critics said the House Speaker had been in office too long, had become a creature of the partisan establishment.

Cathy McMorris Rodgers, for 12 years now the district’s representative in Congress and seeking another two-year term in November, serves as chair of the House Republican caucus. As leader, she votes reliably for the GOP’s side in the standoff that rules Washington, D.C. Famously, she voted scores of times to repeal the Affordable Care Act, even as tens of thousands of her low-income constituents were signing up for the health coverage the law made possible.

McMorris Rodgers hails from northeastern Washington, whose counties now suffer some of the highest unemployment in the state: Ferry, 9.8 percent, Stevens, 7.9 percent, Pend Oreille, 9 percent.

Last spring, she announced she would vote for Republican presidential candidate Donald Trump, who notably is a critic of the foreign trade and immigration on which Eastern Washington’s agricultural economy relies.

So why is it the nation’s flyover country — heavily reliant on crop subsidies, fire protection, highway construction, higher education, Medicare, unemployment benefits — has shifted to politicians who have fought for government to spend less, tax less, do less?

For answers and analysis, The Spokesman-Review turned to Cornell W. Clayton, a political scientist who specializes in the study of polarization. He serves as director of the Thomas S. Foley Institute of Public Policy and Public Service at Washington State University.

When Foley and his generation served in Congress, each of the two political parties was divided. Liberals and southern “Dixiecrats” split the Democrats. Republicans included liberals like Oregon’s Mark Hatfield, as well as business and religious conservatives.

To fashion a majority and get anything done, Clayton said, the leaders of Foley’s generation had to work across the aisle. Medicare and civil rights laws of the 1960s, for example, passed with votes from liberals in both parties.

But in a reaction to the enactment of civil rights laws, southern white conservatives left the Democratic Party and joined the Republicans. President Ronald Reagan embraced them in a coalition that also included foreign-policy hawks, the religious right and business groups. That was the coalition Gingrich led to power.

Today’s GOP uses “liberal” as an epithet. Today’s Democrats charge their foes with thinly veiled racism. Political scientists who study roll call votes have found the nation’s elected representatives “are more polarized today than at any time since the 1870s. They’re less likely to vote across party lines than at any time in history,” Clayton said.

Outside the nation’s capitol, Clayton said, Americans have come to identify with parties as if they were tribes. And they show a tribal suspicion — even hatred, at times — toward members of the opposing tribe.

“Partisan identification is mapping onto lifestyle characteristics,” Clayton said. The Republican Party attracts whites, Christians and people comfortable with the norms of rural America. Meanwhile, “Liberals and Democrats live in more urban areas, and they like communities with greater ethnic and religious diversity.”

But what of the need for government services in districts like the 5th?

In fact, Clayton said, the Republican Party’s rhetorical government-bashing has not been matched by shrinkage in government’s size. GOP priorities do shift money from social needs to the military.

“But some of this was just symbolic,” Clayton said. Under Reagan and again under President George W. Bush, “the size of government continued to grow.”

The main thing those presidents cut, he said, is taxes — causing federal debt to grow 161 percent during Reagan’s years and 73 percent in Bush’s.

Meanwhile, the hardening divide between rural and urban led to elections in which only a handful of states are unpredictable. And in these “swing” states, it takes only a small number of voters to change the result.

Tilt one way, there’s war in Iraq. Tilt the other way, there’s the Affordable Care Act.

“There’s a reason why our politics is so angry,” Clayton said. Beyond the points of agreement, “there are real issues at stake and we are closely divided. It’s that close division that frustrates Americans the most. Neither party gets to implement its program.”

Looking back across the nation’s political history, Clayton said, periods of intense polarization occurred when demographic change brought new populations to the table.

The era most comparable to the present, Clayton said, was the 1890s, when similar issues gripped the nation: Immigration was massive and hostility toward the newcomers was intense. Economic opportunity was moving, from local farms to distant corporations. Inequality between rich and poor was so great it spawned passionate populism from the likes of William Jennings Bryan, who alarmed the rich establishment. Big money poured into campaigns.

How does polarization end?

It ends, Clayton said, when one side breaks apart and loses its ability to win elections.

Today’s Democrats, he said, seem to have overcome their divisions and rallied around the leader of their tribe, Hillary Clinton.

But among Republicans, rancor remains. Six months ago, Clayton noted, a majority of Republican leaders felt Trump was unacceptable. “But he was able to take over the party because it was so deeply divided,” between the tea party wing and the party’s old guard, he said.

U.S. Senate candidate Chris Vance, a leader in Washington’s GOP, told The Spokesman-Review Editorial Board that “I’m worried to death about my party.” Trump’s nativism, he said, makes him feel “very concerned.”

But the outcome won’t be Vance’s to decide. On Nov. 8, 5th District’s voters, once again, will leave their mark.