Both studies classify about 10% of the population as "bystanders" who are politically apathetic, identify three Democratic leaning clusters, three Republican leaning clusters, and two other moderate clusters.
In 2005, the Democrats were divided into Liberals (secular and anti-war), Disadvantaged Democrats (social welfare loyalists), and Conservative Democrats (latter day New Dealers). The Republicans were broken into Enterprisers (Staunch conservatives), Social Conservative (religious, critical of business), and Pro-Government Conservatives (struggling social conservatives). The politically involved moderates were classified as Upbeats (positive outlook and moderate) and Disaffected (working class and discouraged).
In 2011, Pew finds two Republican clusters: Staunch Conservatives (highly engaged tea party supporters), and Main Street Republicans (conservative on most issues); three Democratic clusters: Solid Liberals (across the board liberal positions), Hard Pressed Democrats (religious, financially struggling), New Coalition Democrats (upbeat, majority-minority); and three politically active moderate clusters: Libertarians (free market, small gov't seculars), Disaffected (downscale, cynical), and post-moderns (moderate, but liberal on social issues). But, as it discusses in its analysis, the two Republican clusters are very similar to each other, and two of the three political active moderate clusters have weak but clear partisan leanings.
The realignment partially reflects a Republican loss of seven percentage points of population share in favor mostly of moderates, presumably into the Libertarian and Disaffected categories.
According to Pew:
[A] growing number of Americans are choosing not to identify with either political party, and the center of the political spectrum is increasingly diverse. Rather than being moderate, many of these independents hold extremely strong ideological positions on issues such as the role of government, immigration, the environment and social issues. But they combine these views in ways that defy liberal or conservative orthodoxy. . . .
The most visible shift in the political landscape since Pew Research’s previous political typology in early 2005 is the emergence of a single bloc of across-the-board conservatives. The long-standing divide between economic, pro-business conservatives and social conservatives has blurred. . . .
On the left, Solid Liberals express diametrically opposing views from the Staunch Conservatives on virtually every issue. While Solid Liberals are predominantly white, minorities make up greater shares of New Coalition Democrats – who include nearly equal numbers of whites, African Americans and Hispanics – and Hard-Pressed Democrats, who are about a third African American. Unlike Solid Liberals, both of these last two groups are highly religious and socially conservative. New Coalition Democrats are distinguished by their upbeat attitudes in the face of economic struggles. . . .
Libertarians and Post-Moderns are largely white, well-educated and affluent. They also share a relatively secular outlook on some social issues, including homosexuality and abortion. But Republican-oriented Libertarians are far more critical of government, less supportive of environmental regulations, and more supportive of business than are Post-Moderns, most of whom lean Democratic.
Disaffecteds, the other main group of independents, are financially stressed and cynical about politics. Most lean to the Republican Party, though they differ from the core Republican groups in their support for increased government aid to the poor. . . .
[T]he nature of the partisan divide has changed substantially over time.
More than in the recent past, attitudes about government separate Democrats from Republicans . . . In 2005, at the height of the Iraq war and shortly after an election in which national security was a dominant issue, opinions about assertiveness in foreign affairs almost completely distinguished Democrats from Republicans. Partisan divisions over national security remain, but in an era when the public’s focus is more inward-looking, they are less pronounced. . . .
• More Staunch Conservatives regularly watch Fox News than regularly watch CNN, MSNBC and the nightly network news broadcasts combined.
• There are few points on which all the typology groups can agree, but cynicism about politicians is one. Majorities across all eight groups, as well as Bystanders, say elected officials lose touch with the people pretty quickly.
Two of the main issues dividing the Republican clusters are the feeling that businesses make too much in profits and support for environmental regulation, also common in Main Street Republican, both common in Main Street Republicans but not Staunch Conservatives, while they are united on religion, immigration and the view that the social welfare net is too expensive. The Democratic party has more ideological diversity between its clusters.
Particularly notable is the disappearance of the once prominent "pro-government conservative" faction from the Republican clusters. Indeed, both of the Republican clusters and two of the three political active moderate clusters, and at least one of the Democratic clusters are pretty down beat on government in general.
The desirability of environmental regulation has become an intraparty divide for both major American political parties (and amongst different moderate clusters), rather than an interparty divide.