The U.S. Supreme Court turned down a Republican request Monday to block Pennsylvania's new congressional map.
The action deals a blow before the midterm elections to the GOP, which benefited from the previous state district map the party drew. Last month, the Pennsylvania Supreme Court cast aside the state's old map and redrew its 18 congressional districts.
Under the new district map that will likely be in place for November's midterm elections, multiple Republican-held seats would become more competitive. Democrats hope gains in the state will help them win the 24 GOP-held seats needed to take a House majority.
Republicans in the state legislature opposing the map argued the Democrat-majority court unfairly drew the lines for partisan gain. Earlier Monday, a panel of federal judges in Pennsylvania also declined to block the map.
The state's primary elections will take place May 15. Candidates are already in the process of working their way on to the primary ballot. Some who are seeking office could have found themselves in different districts depending on which map was in effect in November.
Several Pennsylvania districts previously held by Republicans are considered competitive later this year under the new map. Strong special election performance by Democrats, most recently in southwestern Pennsylvania, and a string of retirements has increased GOP worries about holding on to enough seats to keep a House majority.
Here are the expected battleground districts in Pennsylvania in November: