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Democratic gubernatorial candidate Tony Evers, left, and lieutenant governor candidate Mandela Barnes claim victory at their watch party, early Wednesday, Nov. 7, 2018, at the Orpheum Theater in Madison, Wis. Gov. Scott Walker narrowly lost his bid for a third term to Evers. (Mark Hoffman/Milwaukee Journal-Sentinel via AP) ORG XMIT: WIMIL281
Mark Hoffman, Milwaukee Journal Sentinel

Tuesday's election results gave Democrats control of the House of Representatives for at least the next two years. But their success elsewhere on the ballot puts them in a better position to control it for the next decade after that.

With Democratic candidates for governor and state lawmaker winning in several key states, the party broke Republican monopolies that redrew the political maps after the 2010 census – maps that have given the GOP an advantage in congressional elections in the years since.

On Tuesday, Democrats picked up full control of state governments in Colorado, Illinois, Maine, New Mexico, New York and Nevada.

In several states where Republicans held full control – Kansas, Michigan, New Hampshire and Wisconsin – they will now share power with Democrats.

Most of those states will hold state legislative elections again in 2020. But Democratic wins this year will strengthen their hand when states face the once-a-decade task of redrawing the congressional district lines in 2021.

Elsewhere, voters approved ballot initiatives aimed at reforming redistricting by taking it out of the hands of politicians. Michigan, Colorado and Missouri all passed redistricting proposals. A fourth initiative, in Utah, appears to be passing narrowly.

More: Midterms: Races for governor, statehouses help decide control of Congress for a decade

"The Republicans are on notice that the playing field and the rules will be different after 2020," said Jeffrey Wice, a Democratic redistricting attorney.

Republicans are not conceding anything. No matter who draws the maps, they say, Democrats still have yet to prove they can consistently win elections outside major cities. 

The GOP still controls 62 of 99 state legislative chambers (every state has two houses in their legislature except Nebraska), and the Democratic gains Tuesday were in states that Hillary Clinton won in 2016.

"They have not shown an ability to get beyond their base states and get into purple states – much less red states," said Matt Walter, president of the Republican State Leadership Committee. "They're only talking about redistricting as an excuse for their failure to run good candidates and win elections."

Still, Democrats made progress on Tuesday.

They picked up seven governorships, including in the gerrymandered battleground of Wisconsin. While Republicans solidified their control the Wisconsin legislature, Democrat Tony Evers will be able to use his veto on Republican-drawn maps.

Other Democratic governor pickups were in Illinois, Kansas, Maine, Michigan, Nevada and New Mexico. 

In Minnesota, the Democratic-Farmer-Labor party took control of the House of Representatives, giving it a stronger hand in redistricting.

Democrats also took back a legislative chamber in Colorado, Connecticut, Maine and New York – potentially giving them monopoly power over drawing maps in those states. In New Hampshire, they took back both chambers.

In Michigan and Pennsylvania, Democrats broke Republican super-majorities in the state Senates. That's important because it will allow them to sustain vetoes from their Democratic governors. 

"It’s a long game, but we gained a lot of yardage," said Kelly Ward, executive director of the Democratic National Redistricting Committee. "Now we have the real potential of a one-two punch of 2018 plus 2020 – to take these gains and continue them in a presidential election year."

Most governors are elected to four-year terms, so the winners Tuesday will be in office when maps are redrawn in 2021. But most state legislatures will have more elections in 2020, giving the parties one more round to fight at the ballot box.

Until then, the battle over redistricting will shift to courtrooms around the country.

Democratic groups are challenging a Census Bureau decision to include a citizenship question on the 2020 census form. They say it's meant to discourage immigrants from standing up to be counted.

The 10-year population tally begins the process of drawing political maps across the country. First, the 435 congressional seats are allocated among the states based on their population. Then the states draw districts, making sure each has roughly the same population.

In drawing their maps, the states also have to comply with the Voting Rights Act, state constitutional provisions and a growing number of state and federal court rulings. 

Just this week, a federal court struck down Maryland's congressional map as an unconstitutional gerrymander. That ruling went against Democrats, who drew Maryland's map in 2011.

That map extended a district that had been based in rural Western Maryland, a Republican stronghold, down into the Washington suburbs, which are dominated by Democrats.

The effort worked: In the next election, Democratic banker John Delaney, a political newcomer, easily ousted longtime Republican Rep. Roscoe Bartlett. The party has held the seat ever since.

Democratic businessman David Trone won Maryland's 6th District on Tuesday. But after the court ruling the next day, he'll have to defend a redrawn seat in 2020.

The new Maryland map will be drawn by the state lawmakers or, if they fail, a court-appointed commission. 

How big of a difference do court-drawn maps make?

Across the Mason-Dixon Line in Pennsylvania, Democrats had been unable to beat a single incumbent Republican congressman in a general election since 2010.

That changed after the Pennsylvania Supreme court struck down the Republican-drawn map this year and drew its own.

On Tuesday, four Democrats – all women – won districts in suburban Philadelphia, flipping them from red to blue and breaking up what had been an all-male Pennsylvania congressional delegation.

More: Pennsylvania women break record, make history in 2018 midterm election

"Tonight's not about one candidate and it's not about one party," Rep.-elect said Susan Wild at her victory party. "It's about our entire community rising up and demanding representation that will fight for all of us." 

Contributing: Patrick Marley and Molly Beck in Madison, Wis., Kathleen Gray in Detroit and Candy Woodall in York, Pa.