Pennsylvania’s Supreme Court released a new congressional map for the Keystone state on Monday afternoon and in the process gave Democrats a likely major boost in their efforts to win back control of the House of Representatives this fall.

The redrawn map—which was offered as a legally mandated fix to the heavily gerrymandered prior lines—reshapes the state such that, according to Cook Political Report’s Dave Wasserman, there are now eight Hillary Clinton districts and 10 Donald Trump districts. President Trump won the state in the 2016 election by less than 1 percentage point. There are currently five seats held by Democrats and 12 by Republicans, with one vacant.

The map is likely to be the most significant midterm election development until the actual election itself, seriously enhancing the likelihood that Nancy Pelosi regains her gavel as speaker. For that, and other reasons, it is also likely to draw a legal challenge from Republicans in the state.

The new map moves districts from Republican-dominated to lean-Democratic while tightening some districts that remain in GOP hands. The open seat in Republican Rep. Pat Meehan’s vacated 7th congressional district is now rated as safely Democratic but Republican Rep. Ryan Costello’s 6th congressional district and Rep. Keith Rothfus’ 12th congressional district have become much more Democrat-leaning in this new map.

Retiring Republican Rep. Charlie Dent, who represents the state’s 15h congressional district, is now defined as a Clinton district.

While the map does not affect the most imminent election in Pennsylvania—a special election contest between Democrat Conor Lamb and Republican State Representative Rick Saccone—the redrawing creates a scenario in which the winner would possibly have to run in a different district in November (should he pursue re-election).

The Pennsylvania Supreme Court had to issue the new map after Republican lawmakers and Democratic Gov. Tom Wolf could not come to an agreement on a substitute map by Feb. 15. Wolf dismissed the initial map presented to him by Republican leadership last week saying: “Partisan gerrymandering weakens citizen power, promotes gridlock, and stifles meaningful reform.”

In response to this newly released map, Wolf said in a statement that he “applaud[s] the court for their decision and I respect their effort to remedy Pennsylvania’s unfair and unequal congressional elections.”