In a Feb. 22, 2011 photo, CWA Union member Paul Solano, left, joins other union members and supporters as they shout down rival protesters in Denver. (JOHN PRIETO/AP)

Across the political spectrum, from right to left and among the unaligned, Americans have become more doctrinaire and ideological in their political views, according to a major new study by the Pew Research Center.

Staunch Conservatives and Solid Liberals, two groups identified in the study as having strong allegiance to the Republican and Democratic parties, respectively, are more ideologically consistent internally while sharing almost nothing in common with each other on major political issues. Those findings are emblematic of the deep polarization that now shapes U.S. politics.

Among the growing segment of Americans who identify with neither party and call themselves independents, there are fewer moderates. Many in the “middle” hold strong, ideological views. The study concluded that three groups in the center of the Pew typology “have very little in common, aside from their avoidance of partisan labels.”

“What we see is a much bigger and increasingly diverse middle,” said Andrew Kohut, president of the Pew center. “What’s striking about it is that they’re not so moderate. People in the middle have some strong, well-defined ideological points of view.”

The survey also provides a fresh take on a still smoldering question about the decisive Republican wins in 2009 and 2010: Did voters change their minds following Democratic victories in previous elections, or did left-leaning voters simply decide to sit out the midterms?

The ultimate answer — with its major implications for upcoming elections — has eluded analysts and potential office-seekers alike. The Pew study suggests that the composition of the electorate was a somewhat bigger factor than the changing views among those who voted in both elections.

The Pew study offers a political typology of the nation. It is the fifth such study since Pew began the project in 1987 and, as with past studies, provides a wealth of data and insights into the state of politics. Pew breaks down the current electorate into eight politically engaged groups and one group largely on the sidelines, based on their party identification, values and attitudes on major issues.

The study highlights fissures that cause tensions within each party’s base. More broadly, it points at the coming clash in 2012 that will test the staying power of a conservative movement that flexed its muscles in 2010 against the strength of the coalitionBarack Obama assembled to win the White House in 2008.

Michael Dimock, a Pew Research Center associate director, provided examples of the growing gulf between liberals and conservatives. One example concerned the question of whether government should do more to help the needy, even if that means bigger deficits, or whether government cannot afford to provide that assistance. The survey found a 65-point gap between liberals and conservatives. Six years ago, the gap was 52 points.

When the Pew center last undertook a mapping of the electorate, foreign policy represented the major split between Republicans and Democrats. Today, the most significant divisions that shape the electorate are the size and scope of government and President Obama himself. (The survey was completed before the killing of Osama bin Laden on Sunday.)

Pew categorized Republicans into just two groups, Staunch Conservatives and Main Street Republicans, one group fewer than in 2005. The authors said the change reflects the consolidation of economic and social conservatives into one bloc, sharing deeply conservative views on almost all issues, and a shrinking of the Republican base.

Pew identified three Democratic groups: Solid Liberals, Hard-Pressed Democrats and New Coalition Democrats. It also identified three groups not affiliated with either party: Libertarians, Disaffecteds and Post-Moderns. As a practical matter, however, the eight groups have divided evenly between Democratic and Republican candidates in their voting behavior in the past two elections.

Several key groups shifted toward the GOP between 2008 and 2010. But those gains also resulted from the fact that some Democratic groups turned out in lower numbers. With one important exception, those shifts among voter groups appear poised to reverse themselves in 2012.

Voters on opposite ends of the spectrum hardly budged between 2008 and 2010. In the other five groups, which make up 58 percent of the electorate, the GOP picked up an average of 13 percentage points between 2008 and 2010.

The more Democratic-leaning groups were also apt to participate in lower numbers in 2010, while the three most conservative-leaning groups saw an average rise of five points. These differences largely subside when Obama is squared up against an unnamed Republican opponent in a hypothetical matchup.

Obama obviously will have to contend with an actual Republican opponent. In addition, one important voting bloc continues to trend Republican: libertarians. Seventy percent say they’d back any Republican against Obama. Barely more than half say they voted for McCain in 2008.

Polling manager Peyton Craighill contributed to this report.