In summary What does political polarization look like in the California Legislature? It looks like this chart.

Updated September 19, 2019: The charts and figures in this article were update to reflect all votes in the 2019 legislative session.

What does political polarization look like in California?

Sometimes you can see it in the news, where state lawmakers might seem as focused on the latest inter-party national debate as they are on practical matters of the Golden State.

Or you can see it on the floors of the California Assembly and Senate, where this year state lawmakers have voted to pass an annual budget, ban home-assembled “ghost guns” and demand that all presidential candidates publish their tax returns—with every Democrat an “aye” vote and every Republican a “no.”

You can see it in last year’s election results too, where the state’s remaining Republican congressional districts appear as blood-red as ever, while Democratic-dominated population centers along the coast continue to skew further blue.

And, with a little bit of number crunching, you can see it in a chart. Like this one:

By analyzing every legislative vote in every committee on every day of each legislative session going back to 1993, a picture of the ideological divisions that shape our state’s politics emerges.

It’s a pretty simple picture.

On the left side of the political spectrum, mostly clustered at the edge: the Democrats in blue. On the right, somewhat more spread out but mostly packed into their own partisan huddle: the Republicans in red.

State lawmakers still have a week to go before the end of this year’s session. Many of the year’s most controversial bills still have to be debated and voted upon. But with 8,740 roll calls behind them already, it might be a little late for the 2019 Legislature to break its sectarian streak.

This isn’t exactly a new trend. Though political independents and bipartisan-curious members of both parties populated the corridors of the Capitol throughout the 1990s, the state Legislature has been more or less neatly divided between “R” and “D” since the turn of the millennium. That’s despite a series of recent reforms — including an independent commission to draw districts and the non-partisan “top two” primary — that the state enacted to inspire moderation.

Which legislators fall closest to the moderate midpoint? In the Assembly, it’s Huntington Beach Republican Tyler Diep and Bakersfield Democrat Rudy Salas. In the Senate, its Diamond Bar Republican Ling Ling Chang and Sanger Democrat Melissa Hurtado.



A caveat: The tool used to create these ideological scores doesn’t capture one important quirk of the California lawmaking process: the strategic “no recorded vote.” (More about that below.)

Behind the numbers

The analysis here uses software cooked up by political scientists at UCLA, USC, the University of Georgia and Rice that takes legislative vote data and boils it down to an ideological value (they assign values on a -1 to 1 scale, but we’ve converted them from 0 to 100, with 50 as the midpoint between left and right).

Other methods of measuring a particular lawmaker’s political leanings might judge legislators by their votes on a particular set of bills or use scorecards from left- or right-leaning interest groups. Instead, this method takes into account thousands of “aye” and “no” votes, employing an algorithm that clusters legislators based on how frequently they vote with one another. The result is a kind of ideological map, said Jeff Lewis, a political scientist at UCLA who helped develop the model.

“People located more closely together on the line are people who vote more similarly,” he said. “The idea is to reduce the thousands, or in this case, maybe even tens of thousands, of voting decisions that each member makes into a single number that characterizes their voting patterns relative to other members.”

By analogy, you can think of each legislator’s ideological position like a coordinate on a map.

Let’s say you’re clueless about California geography and have an even worse sense of direction. Someone tells you that Redding is 660 miles from San Diego, while Fresno is about 330 from both. Without consulting a map or knowing north from south, you’d still be able to say that Fresno is roughly right in between Redding and San Diego.

In the same way, the algorithm “takes the matrix of distances” between voting patterns and “tries to make a map,” said Lewis.

The result, when applied to this year’s roll call data and layered atop an actual map of California, is a Golden State with navy blues coating the coasts, crimson streaks blazing the interior and very few splashes of purplish pigment in between.

(To make optimal use of these charts and maps, you’ll need to know your legislators’ names, and/or your Assembly or Senate district numbers. You can find that information by putting your address into this state tool. Then check out the ideological scores of your lawmakers on the maps below:)

Party above all

While moderate legislators still exist in either party, the “D” or “R” after their names still says a lot more about how they tend to vote than the politics of the district they represent or their past voting record.

Case in point: Assemblyman Brian Maienschein.

During the last legislative session, Maienschein was a Republican representing a patch of suburban San Diego County that once went predictably Republican, but like so much of coastal Southern California in the age of Trump, has been shading purple. In the 2018 election, Maienschein narrowly kept his seat. He then promptly switched parties.

If party were just a letter, one would expect Maienschein to occupy roughly the same ideological area this year as he did in the 2017 session despite his new affiliation. And while it’s hard to make direct comparisons across years, that doesn’t seem to be the case.

As a Republican, Maienschein was the most liberal of his fellow caucus members in the Assembly, but still sat far to the right of any Democrat. This year, his voting record has placed him to the left of 13 Democrats.

The assemblyman did not respond to requests for comment.

But he’s hardly an outlier.

Across California, Democratic lawmakers represent a wide swath of ideological terrain, from bluest Berkeley to Huntington Beach, where registered Republicans still outnumber Democrats.

But for all that diversity, most Democrats still vote with their party most of the time. According to Lewis, that partisan clustering is predictable for a number of reasons—some of which have nothing to do with ideology.

For one, legislative leaders—the Speaker of the Assembly and the President Pro Tem of the Senate—have a lot of power in Sacramento. They assign committee positions, dole out office spaces and generally have sway over whether a bill moves forward or is buried in committee.

“When leadership comes and tells you to vote for something, you probably want to have a pretty good reason not to,” he said. As a result, even legislators who are centrist at heart will pick their battles when deciding when to break with their party.

But partisan voting patterns in the Legislature also reflect how Californians vote.

The state officially holds a “non-partisan” primary for non-presidential candidates, in which a registered voter can cast their ballot for whomever they like regardless of party affiliation. But the state’s primary electorate is disproportionately made up of loyal Democrats and Republicans, with independents and the politically uninformed staying home. Candidates often have little reason to appeal to the political center, because the center generally doesn’t show up.

“You could imagine (moderate Democrats) trying to stave off a challenge from someone on their left rather than someone on their right,” said Lewis.

As a result, even in a relatively moderate district, Democratic lawmakers may tend to skew progressive in their voting habits.

What might be missing

When a lawmaker chooses not to support a particular bill, but doesn’t want to vote “no” outright, they have the option to abstain.

Why the pretense? Maybe a “no” vote will make the lawmaker look bad with constituents. Maybe it will antagonize the legislative leadership or the bill’s interest group backers. Maybe it’s just a way of being polite to the bill’s author.

The ideological scoring algorithm used in this analysis cannot distinguish between a real “no recorded vote” (maybe the lawmaker just had to go to the bathroom) and one used to duck a tough vote. So it simply ignores them.

By skipping what are effectively “no” votes on controversial bills, in which a lawmaker breaks from his or her own party, the method might be overstating how often lawmakers from the same party vote together. In other words, the Legislature may be less divided along partisan lines than it seems.

Moderate lawmakers do tend to skip votes more often than their colleagues at the ideological edges. Maybe that’s just a coincidence. Assemblyman Ken Cooley, a Democrat from Rancho Cordova, caught pneumonia in the middle of the legislative session. Joaquin Arambula, a Fresno Democrat, took an extended leave from Sacramento to fight a misdemeanor child abuse charge over which he was cleared.

But there is a pattern.

Lewis said that he has never studied the phenomenon in California. But when he and his fellow researchers looked at similar legislative sleights of hand (such as in the Illinois capitol), they didn’t have much effect on the results.

Nonetheless, if every “no recorded vote” from California legislators were to be treated as an actual “no,” here’s how the spectrum would change: