This change in recent years has been significant. The percentage of Republicans identifying as conservative on both dimensions has dropped 15 percentage points since 2012, largely offset by an increase in the percentage who identify as moderate or liberal on both dimensions.
Your response -- if you have been paying any attention at all -- is WHAT? After all, the race for the Republican presidential nomination in 2016 has, to date, largely been a battle over which candidate can portray themselves as the most conservative. And, there's tons of statistical data that suggests that Republicans in Congress have moved sharply more conservative in recent years.
These two things seem to make no sense at all. How can the percentage of Republicans defining themselves as both fiscally and socially conservative be at a decade-long low even as GOP politicians seem to be falling all over themselves to build conservative-as-they-come resumes and voting records?
The answer is contained in this analysis by Newport (bolding mine):
A GOP candidate positioning himself or herself as conservative on both social and economic issues theoretically will appeal to less than half of the broad base of rank-and-file party members....The caveat in these campaign decisions is that not all Republicans are involved in the crucial early primary and caucus voting that helps winnow the pack of presidential candidates down to a winner. Ideology on both social and economic issues is strongly related to age, and primary voters tend to skew older than the overall party membership. This could benefit a more conservative candidate in the primary process, but that advantage could dissipate in the general election.
Politicians -- and this will be some breaking news -- tailor their messages to the people who they believe will turn out to vote. And, history suggests that the likeliest voters tend to be the truest of true believers in your party's base. They are the ones who prioritize voting -- every time and always.
That's especially true in states like Iowa and South Carolina, which will cast two of the first three votes of the 2016 Republican presidential primary season. In Iowa in 2012, 57 percent of GOP caucus attendees described themselves as evangelical or born again; that number was 65 percent in South Carolina. The truth of the matter then is that the men and woman who want to the be the GOP nominee don't really care all that much about the fiscally conservative/socially moderate Republicans living in the other 48 states. To win the Republican presidential primary, you need to win conservative voters. Everyone else, theoretically, will come along for the ride.
That basic dynamic -- with a bit of a twist -- explains what's going on in the growing partisanship among Congressional Republicans too. Two straight decennial redraws of the 435 congressional districts in the country have largely solidified the partisanship of the House seats in the country. That means that the path to Congress for most Republicans (and, to be fair, Democrats) is to make the base happy. Just like at the presidential level, the most conservative voters tend to be the ones who vote in downballot contests -- meaning that if you are seen as the most conservative person in a race, you are very likely to win. The only danger to an incumbent Republican in most of the districts in the country is a primary challenge from their ideological right. Given that, Republican incumbents do everything they can to compile as conservative a voting record as possible while in Congress.
There's one critical difference between the rightward movement of candidates running for president and those running for the House: The former group has to worry about winning a general election among a roughly evenly-divided national electorate.
If both the country as a whole and the Republican party are moving away from pure conservatism -- particularly on social issues -- that translates to a massive gap between what it takes for a GOP candidate to win a presidential primary and what it takes for that same candidate to win a presidential general election. That gap was what Jeb Bush was trying to speak to when he said famously/infamously:
I kinda know how a Republican can win, whether it's me or somebody else -- and it has to be much more uplifting, much more positive, much more wiling to be, 'lose the primary to win the general' without violating your principles. It's not an easy task, to be honest with you.
No, it's not. Welcome to the central challenge for Republicans heading into 2016.