New congressional maps passed by Virginia voters could allow Democrats to flip as many as four House seats and tilt the party toward retaking control of the US House of Representatives in November.

Virginia backs new maps in narrow vote

Virginia voters have approved a redistricting measure that redraws the state's congressional boundaries, a result that could improve Democratic prospects in November's midterm elections. The measure passed 51.4 percent in favour to 48.5 percent against.

The new maps could allow Democrats to flip as many as four House seats, potentially making it easier for the party to take control of the US House of Representatives.

President Donald Trump called the outcome "rigged" following the result, though he did not provide evidence to support the claim.

Part of a national redistricting battle

The Virginia vote sits inside a broader, intensifying fight between Democrats and Republicans over the drawing of electoral maps across the country. Experts have warned that the unprecedented pace of tit-for-tat redistricting actions risks a surge in gerrymandering that could ultimately harm voters rather than parties.

The national contest has reached the US Supreme Court. The court recently reinstated a Republican-favoured Texas electoral map that, according to those who challenged it, could flip key districts to Republicans. The court has also moved to limit the use of race in drawing electoral maps, a decision critics say will make it harder to challenge maps that dilute the voting power of racial minorities — a outcome described as a significant blow to the Voting Rights Act.