Two Southern California Republican Congressmen, Ed Royce and Darrell Issa, recently announced their retirement. Advantage Democrats? Maybe. Maybe not.

The first reaction to the news that these two GOP stalwarts won’t be seeking re-election in traditionally safe Republican districts (but districts that Hillary Clinton carried in 2016) was that these seats could swing toward the Democratic column (The Cook Political Report quickly switched its prognosis for the Royce seat from “Leans Republican” to “Leans Democratic.”). But the arithmetic may be more complicated than that.

While Orange County has been moving from deep red to light purple, Republicans still hold a registration edge (albeit from low- to mid-single digits) in both these districts

Non-incumbent Republicans won’t have the albatross of the national GOP hanging around their necks.; they won’t need to defend their votes on health care or tax reform to a swath of disgruntled constituents. Issa, while still contemplating re-election, did vote against the tax reform measure that socks it to California. Royce towed the party line on both hot button issues.

Running for reelection, Congressional incumbents enjoy clear advantages in name-recognition and fund-raising, but GOP insurgents may have an easier time distancing themselves from their highly unpopular President than sitting Republicans who have pretty much had to follow the leader’s line.

California’s “top-two” primary system, coupled with a No Party Preference (NPP) registration of roughly 25% in each district, plays into the electoral uncertainty in the races to replace both Issa and Royce. With a bevy of Democratic contenders —and maybe a NPP candidate or two–vying for a place in the November runoff, it is conceivable that two Republicans could end up facing off in the General Election. It has happened before.

For example, travel back in time to the 2012 election. In the top-two primary, Congressman Gary Miller, running for re-election as the incumbent in the newly drawn 31st Congressional District, faced one strong GOP opponent, State Senator Bob Dutton, and four Democrats. The favored Democrat in this then-49% Latino and plurality Democratic district was Redlands City Councilman Pete Aguilar. But the Democratic primary vote split enough that Aguilar came in third, leaving two Republicans to face-off in the November run-off.

And what happens if a moderate Republican, say like Assemblymember Rocky Chavez–who’s already announced for the Issa seat, ends up facing a hard-left Democrat in November?

There are other districts where a Republican cast change could help the GOP. Rep. Dana Rohrabacher is a prime target with his pro-Putin image and quirky persona and policy stands. Despite a solidly Republican district, Rep. Duncan Hunter, Jr. is on the Democrats’ hit list because he is carrying a truckload of baggage over his campaign finance maneuvers. Fresh Republican faces could make these seats less vulnerable for the GOP.

On the other hand, many pundits insist that 2018 is shaping up to be a banner year for Democrats, particularly in California. Vehement dislike of Donald Trump has energized key Democratic constituencies, including women, ethnic voters and Millennials. The Republican brand is severely tarnished.   A national Democratic wave is likely to produce a California tsunami. At this point, it appears unlikely that the GOP will have a standard-bearer in November for either the gubernatorial or U.S. Senate race.   High Democratic turn-out and lukewarm Republican participation is a recipe for a Democratic sweep.

Certainly, the trend line for California Republicans has been straight downhill. Democrats now hold a 19-point registration advantage over the party and the GOP is about to be overtaken by No Party Preference registrants. Because the NPP voters tend to be younger and include more minorities, this state’s independents lean toward Democratic candidates–or, more precisely, away from Republicans. It is not a coincidence that no Republican has won a statewide election in California for more than a decade.

It remains to be seen whether Republicans can hold the Royce and Issa seats—or any of the other contested districts—but there is a strong indication that Congressmen Royce and Issa were looking to duck the tribulations of a very bumpy political ride in 2018.