Washington (CNN) The Pennsylvania Supreme Court released new congressional district lines Monday, replacing the old Republican-drawn maps in time for the state's May primary.

House Republican and Democratic operatives said Monday afternoon they are still analyzing the partisan makeup of the new districts.

But in a swing state where Republicans hold 13 House seats to Democrats' five, the balance appears all but certain to tip in Democrats' direction.

The biggest changes come in the Philadelphia suburbs, where three Republican-held seats -- Reps. Ryan Costello, Brian Fitzpatrick and the retiring Pat Meehan -- were already Democratic targets.

The new maps appear more compact and suburban than the existing district boundaries and an alternative that state legislative Republicans had submitted -- and one of those districts is now made up of just Montgomery County, a Democratic stronghold that the GOP had proposed dividing heavily.

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