Arnold Schwarzenegger swept into the California governor’s office in 2003 as a Republican vowing to practice what he called “post-partisan” politics.

He was the architect of the state’s nonpartisan redistricting system, which puts an independent commission, not Republican or Democratic lawmakers, in charge of drawing California’s political maps once per decade.

His success in weakening gerrymandering in California is one of the key legacies of Mr. Schwarzenegger’s seven-year tenure as governor. In the world of redistricting reform, he is an unlikely evangelist. After leaving the governor’s office, he lobbied other states to adopt nonpartisan systems and filed an amicus brief when the U.S. Supreme Court took up a landmark case on gerrymandering.

Now, Gov. Gavin Newsom, a Democrat, has floated a plan to put Mr. Schwarzenegger’s independent system on hold for the rest of the decade in favor of a set of maps that benefit Democrats. Mr. Newsom’s proposal is a response to President Trump’s efforts to get Texas to draw new districts that would help Republicans win more seats in Congress.

On Friday, Mr. Schwarzenegger’s top aide gave the first indication that the former governor could jump into the national fight over redistricting to try to save the system Mr. Schwarzenegger championed in California.

“His position is that two wrongs don’t make a right,” Daniel Ketchell, Mr. Schwarzenegger’s chief of staff, said in an interview. “He is still committed to independent redistricting in every state around the country. He thinks we have to get rid of gerrymandering to get rid of gridlock and have politicians who actually care about what the people think.”