SAN FRANCISCO (KCBS)— California’s top-two open primary is getting its first true test as its use expands to statewide offices for the first time. One of its biggest impacts may be in helping Republicans choose which of their candidates will face Governor Brown in November’s election.

The top-two system went into effect in 2012, producing several legislative races where politicians faced off against candidates from within their own party, since the top-two advance regardless of party.

READ MORE: Redwood City Sets Up Vaccination Clinic for Special-Needs Community

With Governor Brown expected to take first place in a landslide, University of San Francisco Politics Professor Corey Cook said some Democrats may decide to meddle in the GOP race instead, casting ballots for either Tea Party conservative Tim Donnelly or the more moderate Neel Kashkari.

READ MORE: Parishioners of Burned Concord Church Stay Committed to Helping Homeless

“Presumably the big impacts this time around will be, at least on the statewide level, that you’ll see any ability to sort of crossover vote, where you have Democratic voters voting in Republican primaries essentially and vice versa.

Cook sees about 18 congressional and legislative races where the top two are likely to be from the same party, so instead of the primary winner coasting to November victory in a lopsided district, those two will have to spend millions more to slug it out again.

MORE NEWS: San Francisco Homeless Camp to Be Removed Monday, Advocates Say Residents Have Right to Stay

“Now they’re going to be re-running the race in November. It’s a campaign consultant’s dream,” Cook said.