Americans’ votes for Congress are heavily dependent on where they live, with suburbs a battleground this year in between Democratic cities and Republican rural areas. But those same demographic trends are also affecting less prominent elections than the battle for Congress: the thousands of races for state legislative seats around the country.

To understand how, CityLab applied its Congressional Density Index to state legislative races in one battleground state, Minnesota, where Republicans are defending an 11-seat majority in the state House of Representatives—a defense being waged primarily in suburban districts.

Minnesota features one major metropolitan area, the Twin Cities of Minneapolis and St. Paul, where a slight majority of the state’s population lives, and then a vast array of smaller cities and towns scattered throughout the state. Minnesota’s 134 state House districts match up with patterns CityLab saw at the congressional level:

• Republicans dominate the 29 “pure rural” districts, where Trump won an average of 62.5 percent of the vote and Republicans control 25 seats in the House.

• Another 27 districts have a mix of rural areas and denser towns; Democrats do slightly better here, with six districts to Republicans’ 21, but are still a minority.

• Democrats represent all 16 of the “pure urban” districts, where Trump got just 13 percent.

The battle for the state House will come down to Minnesota’s 62 predominantly suburban districts, which fall into two general flavors. The 36 “dense suburban” districts, where homes tend to be closer together, lean Democratic: Trump averaged just 37 percent of the vote here. Democrats see the nine of these anti-Trump districts still held by Republicans as prime pickup opportunities.

But if Minnesota Democrats are to win the House, they’ll have to win some seats in less friendly territory, too: the “sparse suburban” districts, where Republicans hold the overwhelming majority of the seats, and Trump averaged 47 percent of the vote. These are winnable districts for Democrats, but it won’t be easy. Sparser parts of the state vote more solidly Republican, even when they didn’t vote for Trump.

Campaigns understand the importance of the suburbs. An analysis of campaign finance data by MinnPost’s Greta Kaul found the highest political spending in suburban legislative races, especially the districts on the edge of the metro—”sparse suburban” districts.

Statewide candidates for governor, U.S. Senate, attorney general and other races are also stumping hard in the suburbs, because of how big and closely divided the electorate is there. In 2016, Hillary Clinton’s lead in Minneapolis and St. Paul was countered by an equally large deficit outside of the metro. She won the state because she eked out a narrow victory in the suburbs.

As a varied, closely divided state, Minnesota is also seeing some important action outside the suburbs. That includes two rural congressional districts, Minnesota’s 1st and 8th, where Republicans are trying to replace departing Democratic incumbents. Some Democrats still hold legislative seats in rural parts of the state and are top targets by legislative Republicans who want to offset any potential losses in their suburban districts.

But with more than half the state’s population (and rising) living in the Twin Cities metro area, it’s the suburbs that are ground zero for the election in Minnesota—and the rest of the country.