They will face off in a special election on Sept. 24 in an unusual runoff: A nonpartisan versus a Democrat. The election will be closely watched because the Democratic supermajority in the Assembly could be affected by the outcome.
In Tuesday's election, Leon recently dropped his Republican registration to run in the assembly race as a nonpartisan candidate. He received 25.1 percent of the primary vote. Rodriguez is a Democrat who secured the endorsement of the California Democratic Party with the support of Sen. Norma Torres. He pulled in 21.6 percent of the vote.
As predicted, turnout in the election was low, with just 8.1 percent of voters in the Los Angeles County portion of the district casting ballots and 9.2 percent on the San Bernardino County side.
Torres vacated the 52nd District seat when she won a special election earlier this year to the Senate's 32nd District. She beat Leon, who ran as a Republican.
The Democratic-dominant district runs from Pomona in Los Angeles County east to Ontario and Chino in western San Bernardino County. The largest geographic block of voters is in Ontario, where Leon joined the City Council in 1999 and has been mayor since 2005.
Democrats won a two-thirds supermajority in the November election, but lost it in June when Assemblyman Bob Blumenfield left to take a seat on the L.A. City Council.
California Democrats have two more chances at regaining the supermajority: the special election primary Sept. 17 to fill Blumenfield's Van Nuys area Assembly seat and the 52nd district seat on September 24.
If the nonpartisan Leon wins, Democrats would remain one seat short of that two-thirds mark.
Correction: An earlier version of this story stated that the special election to fill Assemblyman Bob Blumenfield's seat would be held Sep. 15. In fact, the election will be held on Sep. 17. The story has been updated accordingly.