The Golden Gate Bridge in San Francisco. (Kirby Lee/USA Today Sports)

When it comes to House seats, no state is more consistently Democratic than Massachusetts. The last time that state elected a Republican to the House in either a general or special election was 1994, when Republicans captured 2 of its 10 seats. Over the intervening decades, it hasn’t happened.

But when one is identifying the most Democratic state in the country, Massachusetts usually isn’t the first state that comes to mind. Instead, that honor belongs to California, the nation’s largest state and the one that immediately conjures images of Hollywood liberals and Humboldt hippies. Yet that picture of California is incomplete. Once solidly Republican, the GOP still retains a bastion of support in the southern part of the state, anchored by conservatives in Orange County and the military’s heavy presence near San Diego.

That bastion isn’t as big as it once was. In 2016, Orange County backed Hillary Clinton, the first time the county had supported a Democrat since 1936. This week, two Republican representatives from that region announced that they planned to retire rather than fight for reelection, Reps. Edward R. Royce and Darrell Issa. With an apparent Democratic wave forming for the 2018 elections, that’s not surprising.

But that incoming wave raises an interesting question. Just how close might California get to matching Massachusetts’ Democrats-only House delegation?

Right now, Democrats control 39 of the state’s 53 seats. Here’s the distribution of the seats using Cook’s Partisan Voting Index, a measure of how the districts voted in the past two presidential elections.

The Democrats hold two seats that lean to the Democrats by fewer than five percentage points. The Republicans hold seven that lean to their party by fewer than five points.

That’s out of 14 seats held by the Republicans in total. Eight GOP seats are rated as potentially in play by Cook Political Report, leaving only six seats (outlined below) as safe for the party. Some of the in-play seats, such as Issa’s (rated before the announcement of his retirement) are considered toss-ups, too close to call. Some are probably going to be held by the Republicans, but you never know. Only two Democratic seats are considered in play.

(Every seat to the left of that cluster of outlined, safe-Republican seats is a district that Clinton won.)

So that’s the question. As of this moment, Cook figures that there are:

  • 37 safe Democratic seats
  • Two Democratic seats in play
  • Eight Republican seats in play
  • Six safe Republican seats

Meaning that, should things go the Democrats’ way this November, they could emerge with 47 of the state’s 53 House seats — enough by itself to reduce the Republicans’ 46-seat majority to a 30-seat one.

But those six safe Republican seats may not be that safe.

First of all, it’s important to note that the nature of which seats are in play evolves quickly. One week ago, we would have assumed that Royce and Issa would have the advantage of incumbency going into the 2018 elections, but now we know that their party, for better or worse, won’t.

Last November, we looked at how Cook’s estimates a year before an election had fared; in the last 12 months before the elections of 2006 and 2010, the parties that ended up getting blown out in those elections (the Republicans and the Democrats, respectively) saw huge increases in the number of toss-up seats that they would need to defend. Over the last 12 months of the 2006 race, the Republicans saw 34 seats become toss-ups. In the last 12 months of the 2010 contest, the Democrats added 32.

There’s another complicating factor that could work against the Democrats’ hopes of locking down the House delegation — or for it.

In California, the general election candidates are determined by what’s called a “jungle” primary. All of the candidates, regardless of party, compete for the two general election spots. That has meant, at times, a contest in which a Democrat faces off against a Democrat, as in the 2017 special election for the 34th Congressional District. (This is the House race that President Trump likes to ignore when he touts the Republicans’ special-election successes.)

But it also makes for a complicated dynamic for the parties. The reason is simple. Imagine you have a jungle primary with 10 candidates, two Republicans and eight Democrats, in a district that’s 60 percent Democratic. If those Democratic candidates split that 60 percent of the vote, each gets about 7.5 percent of the vote. If the two Republicans split the 40 percent of the electorate that is Republican, each gets 20 percent — and a ticket to the general election.

This is significant concern for Democrats, for understandable reasons, and one of the factors that makes predicting the successors to Issa and Royce particularly tricky.

The system could also work to the Democrats’ advantage.

On Election Day, the most significant contest in the state will be the election in which Sen. Dianne Feinstein (D) defends her seat. One possible outcome of the primary for that contest is that Feinstein ends up facing off against another Democrat (perhaps state Sen. Kevin de León). In that case, Democrats could have a much stronger motivation to go to the polls than might Republicans.

If Republican turnout is down in a Democratic wave election, and the Democrats avoid a Republican-vs.-Republican general election ballot? All bets might be off.

The district that most overwhelmingly backed Trump in 2016 (using estimates from Daily Kos) was House Majority Leader Kevin McCarthy’s (R). Trump won his district by 22 points, a seemingly insurmountable margin.

In the special House election in Kansas last year, the Democratic candidate lost, but by a 25.2-point smaller margin than did Clinton in that same district. If that happened nationally, which is very unlikely, Democrats would take every seat in California — and 11 other states (including Massachusetts).

One final note. As this post was being written, Cook Political updated its rating for Issa’s seat. It moved from Republican toss-up to Lean Democratic.