House Minority Leader Nancy Pelosi (D-Calif.) after leaving the House floor in February. (Matt McClain/The Washington Post)

Out of every eight members of the House of Representatives, one is from California. Not quite — math problems involving the number 435 don’t often result in clean fractions. But it’s close enough.

The reason for this, of course, is that 12 percent of Americans are Californians, too. Our representative government, like dividing things from the number 435, is imperfect, but it’s usually not that far off. So when 12 percent of the country heads to the polls to figure out which candidates will be on the November ballot to fill the state’s 53 House seats, it’s worth paying attention to.

Let’s start by looking at how California voted in the 2016 general election. Not the presidential vote; that one is obvious. Instead, here’s how each of the House seats went.

There were nine seats won by Democrats after facing a nonpartisan candidate or another Democrat — a function of the state’s top-two primary system, known colloquially as the “jungle primary.” In that system, whichever two candidates do the best in the primary run against each  other, regardless of party affiliation.

Those Democrats who faced Republicans won by an average of 37 points. The Republicans who beat Democrats won by an average of 18 points.

Unsurprisingly, those races that were closest in 2016 are also those that have been determined to be the most hotly contested this year. That’s not uniformly the case, but it is generally.

The Cook Political Report’s race ratings suggest that one seat held by a Democrat is possibly in play in November, though it’s rated as “likely Democratic.” That’s the 7th District.

On the other hand, nine of the 14 seats held by Republicans are considered to be contested. In seven of them, the Republican won by fewer than 20 points in 2016. In two, the 39th and 49th districts, the Republican incumbents decided not to run again.

Why is a race that the Republicans won by 15 points in 2016 in play in 2018? In part that’s a function of the favorable national environment for Democrats. Remember, though, that thanks to the unpopularity of Donald Trump in the state in 2016, half of the districts that elected Republicans two years ago also voted for Hillary Clinton. Those are the first seven Republican districts on the chart above and the seven districts in the box below.

(The presidential vote data above is from Daily Kos.)

What the Democrats are hoping to do in Tuesday’s primary elections is get at least one Democrat into each of those contested races in Republican-held seats. Remember, only the top two advance. So if the Republicans have two candidates on the ballot and the Democrats have a dozen, an evenly split district in terms of voter registration could see two Republican candidates simply because the Democrats split their vote. That’s a concern for Democrats in several of the seven Republican districts identified above: the 39th, 48th and 49th.

There are interesting things happening in other districts, too. Absentee-voter data from California-based Political Data allows us to compare the ballots that have been returned with the presidential vote in each district.

On the diagram below, any dot above the diagonal line has seen a higher margin of Democratic absentee votes returned than the Democratic margin in the presidential race in 2016. Any dot below the line has seen a greater margin of Republican absentee votes returned.

Nearly every dot is under the line. That’s typical for early and absentee voting in California: It skews Republican. But in a handful of districts, the margin of returned ballots is a lot closer to the margins in the 2016 race. Of particular note is the 10th District, a toss-up race where the Democrats may have a slight early-voting edge. Of course, there are also six Democrats vying to face the incumbent, Rep. Jeff Denham (R). That’s the beauty/nightmare of the jungle primary.

The most important thing to know about Tuesday’s election, though, is that we may not know the results for a while. Since 1990, it’s taken an average of 39 days to certify the results of primary, special and general elections in California. The longest gap between the election and the certification came in 2010, when it took 65 days. The shortest was in 2003, after the recall of Gov. Gray Davis (D). That only took a week — but there were only two questions on the ballot.

So we probably won’t know for a while who won all of the 106 general-election slots up for grabs Tuesday evening. Given the number of candidates competing for those slots and the nature of the election, be prepared for a weird few days.