When President Trump set out to force a gerrymander in Texas that would help Republicans keep control of the closely divided House, he argued it was a simple matter of fairness.

“We are entitled to five more seats,” the president said this month.

He got what he wanted from Texas, where the governor on Friday signed a redistricting plan. But the consequences may not be so simple.

With California Democrats immediately retaliating with their own re-engineering that could potentially swing up to five seats in the opposite direction, a redistricting arms race is quickly spreading across the country. That has become a major headache for incumbent members of Congress in both parties, who are concerned about changes to districts they have spent years — some of them decades — figuring out how to win.

On paper, the changes that have been approved or are under discussion could potentially give Republicans a leg up of six to seven seats in what is expected to be an uphill fight to keep control of the House. But redistricting can deliver unpredictable results, and it is uncertain whether this one will ultimately pan out the way either party hopes.

What is clear is that it has created confusion in the already volatile battle for congressional power, with no clear outcome guaranteed for Republicans or Democrats.