Trends in Party ID, 2004–2018

Charles Franklin
Feb 11, 2018 · 6 min read

(Originally a long Twitter thread)

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A deep dive into party id trends. tl/dr: Reps down 3–4 points in 2017, Dems stable. Both parties weaker than in 2004. Just read the charts!

There has been a good bit of discussion about what has happened to party identification, specifically Republican identification since Trump took office. So let’s look and see what the data show.

It is good to look not just at the last year. A longer perspective reveals a lot about partisan change. Also, let’s look at 5 categories: 2 partisans and 2 independents who lean to a party and pure independents.

Back in 2004, Dem & Rep partisans were near parity, with Reps taking a lead around the 2004 election. This was the time of Karl Rove’s hope for a “permanent Republican majority”.

But those hopes faded during 2005 as the GOP advantage disappeared and continued to decline into 2007 when it leveled off at 27–28%, while Democrats fluctuated between 32 and 35%, taking that advantage into the 2008 election.

With Obama in the White House, Democratic partisans in turn began to fade, falling to 29–30% for most of 2010–2018, with a short-lived recovery in the run-up to the 2012 reelection.

The Obama years didn’t lead to a surge among Republican partisans, however. Their 27–29% share held until 2012, declined to 24 in 2013 before climbing back to 28 at the 2016 election.

Since the 2016 election, Republican partisans have slipped from 28% to 24% as of January 7. That 4 point decline brings them back to their low point of the 2004–2018 period. Still, it is a 4 point drop so far, not more.

The big picture for partisans however is that both the Democrats and Republicans have lost partisan faithful over the past 14 years. Democrats are down over 6 points from their high and Republicans are down 12 points from their peak.

So are the parties withering away, like the state? Not exactly. Independents who lean to one or the other party have grown a bit. Republican leaners were barely 10% in 2005–06 but are now 15%.

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Most of that GOP leaner growth came after the 2006 and especially after the 2008 elections. Since 2009 GOP leaners have fluctuated a bit around 15% without consistent trend up or down.

Democratic leaners rose from 13 to 18 from 2005–2007, then declined back to 13 in 2010 and have since climbed to nearly 18% again as of 2018.

So if we judge from partisans alone, the Dems have been completely flat from early 2014 to the present, while Republicans gained about 4 points over 2014 through 2016 only to see all of those gains lost in 2017.

The recent past, from 2015 to 2018 has seen a 2–3 point gain among Dem leaners while Rep leaners are down 1–2 points over that period, though flat since mid-2016.

So if the Dems are mostly flat, and there has been a bit of GOP decline, where have people gone? Pure independents are up recently, by just over 3 percentage points since the 2016 election.

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Pure independents have not grown substantially in 14 years, holding close to their long term 8.2% average until rising slightly after 2014, falling by 2016 and now rising 3–4 points in 2017.

If we define “independents” to include those who admit they lean to a party, there is quite a different story. Since 2004 independents+leaners has grown from 29% to 44% of the population, an impressive 15 point increase.

As we saw above, that rise comes almost entirely from independents who lean to a party, not from those entirely disconnected from either party.

Leaners are not as strong in their partisanship as are pure partisans, though they vote substantially for the party to which they lean. Thus they provide a significant support for their party, but also a somewhat less reliable one.

Combining partisans and leaners, Dems have held a 5 point advantage since mid-2015, wich has grown to an 8 point lead at the beginning of 2018. Republican supporters are now near their recent lows of 2006–2008 at 38–39%.

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Democrats have not seen substantial recent growth and stand a point below their long term average and 5 points below their high of 51–52% in 2007–08.

Bottom line: There is evidence for some erosion of GOP partisanship in 2017 though I think it is more modest decline than some would suggest. That has not been accompanied by any substantial Dem gains in 2017.

The evidence for change in party identification is strong in showing modest movement, and that largely equal between parties when the same individuals are tracked over time.

However, events, candidates and issues may result in more substantial movement under asymmetric forces. That movement is usually evolutionary rather than revolutionary though in rare cases substantial change occurs in short periods.

This is for the geeks who are dying to know. How do the sizes of the various PartyID categories correlate with one another over the 2014–18 period? Have fun.

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For recent evidence on individual change see 1)

and more recent evidence on individual change see 2)

For a recent argument about the effects of declining GOP identification on Trump approval see

Thanks for playing. /fin

Postscript: There is a lot of enthusiasm on Twitter for the notion that Republicans who shift to independent (or fail to participate in surveys, which is not entirely clear) are propping up Trump approval among the remaining Reps. This is the thesis of the last link above to the Peskowitz et al paper, which you should definitely read. See for example this tweet:

But I think the argument that Reps are becoming independents and that is holding up Trump’s approval needs a couple of qualifications. 1. Rep decline is 3–4pts, which is significant but not huge. 2. Rep approval HAS declined & for both mod & con Reps. See these trends from January through December 31, 2017 with Gallup weekly data.

For all Republicans: down 8.6 points

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For those calling themselves “moderate” or “liberal” Republicans: down 11.0 points

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And even for those calling themselves “conservative” Republicans: down 6.7 points

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Each Republican subset is down. -8.6 percentage points among all Reps, -11.0 among liberal/moderate Republicans and -6.7 points among conservative Republicans. Those declines still leave substantial support for Trump, but the declines are clear, not masked or eradicated by departures from the Republican fold.

If the process of departure is inflating Trump support, it is not so strong as to mask measurable decline among Republicans.

(Note that Trump approval flattened out in September 2017 and has been relatively flat since. The above data also end with Gallup’s final weekly update on December 31, 2017. In January and February polls generally showed a modest increase in Trump support, which is not captured in these charts. Gallup has said they will resume posting demographic breakdowns on a monthly basis sometime in February.)

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