There's a hundred-million-dollar battle brewing for control of Congress, but it's not going to be resolved for seven more years, and the battles will take place in lands far away from Washington.

Both Democrats and Republicans think controlling state legislatures in 2020 is one of the most important political battles to fight, mostly for one reason: The power of the pen -- the kind that draws district lines, that is.

North Carolina in 2010 North Carolina in 2010

Five years out, both sides are in a fundraising battle to build war chests of $70 million to $125 million to swing state legislatures their way by 2020, when new electoral maps will get drawn across the country. The Republican State Leadership Committee announced Thursday it's launching RedMap 2020 and aiming to invest $125 million to expand their majority in the statehouses and redraw the nation's electoral lines.

They're playing the long game, but as Republicans showed in 2010, investing in state races is one of the best bangs-for-your-buck to swing Washington the way you want it.

"The implications of the state-level races reach all the way up to the U.S. Capitol," said Matt Walter, the president of the RSLC, which works to keep Republicans in state legislatures.

Redistricting has always been important to the political process, but in an age in which Americans are increasingly polarized -- and technology allows for even-more-effective gerrymandering -- the shapes and demographics of the districts that are drawn is even more decisive when it comes to control of Congress.

Every 10 years, based on new U.S. Census data, states redraw their legislative and congressional districts. In about 43 states, state lawmakers get to decide how to do this. It's an inherently political tool to help create beneficial districts for whichever party's in power.

[The increasingly ugly gerrymandering of America -- in 7 maps]

And in 2010, Republicans showed just how much can be gained from dominating that process. Fueled by millionaire Art Pope, they invested $30 million into winning state legislature battles -- particularly states where the legislature was up for grabs, and it had a say in redistricting. In the grand scheme of politics, that's not that much money -- but it had a huge impact (thanks in part, of course, to the GOP wave year).

Republicans picked up 675 state legislative seats, gaining control of 12 more state legislatures. The GOP in total controlled about three times as many states in the redistricting process -- including many big, swing-y states where the lines are even more fungible and important.

New lines were drawn, and in 2012, Republicans took over the House of Representatives with a commanding 234-201 majority -- despite the fact Democratic House candidates got 1.4 million more votes than Republican candidates. Some analysts think the current map is such that Democrats simply won't be able to win a majority on it, barring a massive wave in their direction.

"It really helped redefine how the American political system looks at the redistricting process," Walter said.

After another great 2014 midterm election for Republicans, the party now controls an all-time high of 68 of 98 state chambers. That's the potential to rewrite a lot of lines.

Sensing a winning game plan, Democrats are getting in now, too. They launched Advantage 2020 last year, a super PAC that hopes to raise $70 million to play exclusively in states where redistricting is on the line. (Compare that with the $10 million they raised in 2010.)

They'll play in state races in more than a dozen states with the end game of capturing "a couple dozen" congressional seats in the midterms of 2022, Advantage 2020 Director Mark Schauer said.

"Once the lines are redrawn in 2021, the Democrats will have a tremendous opportunity to recapture the majority," Schauer said.

Expect the first of the redistricting battles to take place a little closer to Capitol Hill: Control of the Virginia senate is in question in the fall.

You can bet RedMap 2020 and Advantage 2020 will be there, with an eye toward the future.

[One of America's weirdest congressional districts has just been trashed by the Supreme Court]