A blue wave swept into the House of Representatives this fall, flipping 40 seats and giving Democrats control of the chamber in January — and President Donald Trump his first taste of divided government.

But state elections went the opposite way. In every state except one, the same political party will rule the legislature’s upper and lower chambers. Come January, Minnesota will be the only state where Democrats dominate one chamber and Republicans the other.

The last time state legislatures were so unified, it was 1914. And it’s a signal that state politics are only becoming more homogenous.

“It’s kind of amazing,” said Seth Masket, director of the Center on American Politics at the University of Denver. “Increasingly, people are just voting the same party up and down the ballot.”

Democrats captured the majority in six legislative chambers this year, but Republicans held onto most of the country’s legislatures: The GOP controls 30 of the country’s 49 partisan legislatures, while Democrats have 18, according to the National Conference of State Legislatures. (Nebraska has a uniquely unicameral and nonpartisan legislature, though its governor is a Republican.) In Minnesota, the only split state legislature in the country, Democrats dominate the House, while Republicans held onto their Senate majority by a single seat.

But it’s not like Minnesota is a shining example of bipartisanship in an increasingly partisan world. Voters just weren’t given a choice: None of Minnesota’s senators were up for re-election this year. “Had the Minnesota Senate been on the ballot, just as the House was, it would have been unified as well,” said Tim Storey, director of state services for the National Conference of State Legislatures.

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While Trump must deal with Democratic leader Nancy Pelosi at the federal level, single-party state legislatures are primed to easily rubber-stamp new laws. The escalating political polarization between the states could heighten the differences between the country’s patchworked state laws, particularly around controversial issues that transcend state lines, such as abortion, immigration, and gun control. For example, 60 percent of all guns recovered by Chicago police, according to a city report, were first bought in states like Mississippi and Indiana, which have looser gun laws.

“There’s very little chance that the federal government is going to be taking the lead in policymaking,” Storey said. “Who drives the bus at the state level matters maybe now more than ever.”

Lawmakers in newly unified legislatures are already preparing to pass paralyzed policies. Democrats have long controlled New York’s state Assembly and governor’s mansion, but on Election Day, they also won control of the New York state Senate for the first time in a decade. One of their first priorities will be to pass laws strengthening New York’s protections for abortion access and for immigrants, said Linda Rosenthal, a Democratic Assemblywoman who represents the west side of Manhattan.

“There won’t be anyone lobbying against those,” Rosenthal said. “Or there will be, against the abortion one, but now, that’s going nowhere.”

“Increasingly, people are just voting the same party up and down the ballot.”

Democrats did manage to snag seven governorships; now, 13 state legislatures will be headed by governors of the opposite party (who’ll be armed with the power to veto). But the blue wave only trickled into state legislatures, where the GOP didn’t see nearly as many losses as expected. In every midterm cycle since 1902, the party of the president has lost an average of 425 state seats, Storey said. This year, however, Democrats gained just 320 seats. That’s thanks in part to the fact that after Republicans gained at least 680 state legislature seats in the 2010 election cycle, they controlled drawing huge swaths of the nation’s legislative districts.

“Neither party is innocent in maximizing their advantage when it comes to the redistricting process, but they [Republicans] were particularly effective at it,” Storey said. “That is the gift that keeps on giving, every election.”

When state legislatures are so thoroughly dominated by one party, jockeying between Democrats and Republicans matters less than ideological battles within parties, according to Boris Shor, a University of Houston political science professor who’s studied polarization within state legislatures. Over the last 20 years, his research shows, the number of both Democratic and Republican moderates have dwindled, leaving the two parties drifting further away from each other and closer to their party’s ideological extremes.

“It’s not just that the two parties are pulling apart; it’s also that the two parties are becoming more internally cohesive,” Shor said. And sometimes, without an opposite party to fight, the ruling power embarks on some cleansing.

Take Texas, where Republicans have had a “trifecta”— control of the House, Senate, and the governor’s mansion — since 2003. Gov. Greg Abbott, a Republican, tried to take out a moderate member of his own party: He spent hundreds of thousands of dollars in an attempt to topple Houston-based state Rep. Sarah Davis in support of a more conservative candidate.

“Primarying Sarah Davis is the equivalent of like a drug dealer torching cash,” Shor said. “You have so much that torching it is just a display of power.”