Lawmakers in California and Texas - the two most populous US states that together contain more than 70 million Americans - are at the centre of an intense political battle that is poised to have a major impact on the balance of power in Washington DC.
After Texas passed a redistricting measure that would create five more congressional seats favouring Republicans, California lawmakers hit back on Thursday by voting to re-draw the state's maps - carefully made to cancel out Texas' move. The California maps will go before voters in November.
This political arms race for power may seem both bizarre and confusing – but it is one that could spread to other states in advance of next year's national midterm elections.
Here's what you should know about America's fight over congressional redistricting.
The battle began in Texas this summer, when the Republican-majority legislature took the unusual step of re-drawing congressional seats in the middle of the decade - in a deliberate effort to send more Republicans to the House of Representatives in Washington.
