More Americans now call themselves politically independent than at any time in the last 75 years, according to a new poll that shows Republicans and Democrats are more polarized than they've been in a generation.

The findings come from a new Pew Research Center poll that highlights the values gap between the two major parties. The poll finds that 38% of adults call themselves independents. Only 32% of Americans identify themselves as Democrats and 24% say they're Republicans.

Today, there's a difference of 18 percentage points between Republicans and Democrats on 48 questions about political values, such as the role of government, the environment, national security and other subjects. That's up from 10 points in 1987, when Pew first began its studies on American values.

The biggest increases in the partisan gap during the past 25 years occurred during the presidencies of George W. Bush and Barack Obama, Pew finds.

Core supporters in both parties believe their parties don't stand up for traditional party positions: More than seven in 10 Republicans (71%) and nearly six in 10 Democrats (58%), according to the poll.

What does this mean for the 2012 election? Pew notes the largest gap between supporters of President Obama and presumptive GOP nominee Mitt Romney is found in their beliefs about the scope and role of the government in the economy.

"Swing voters, who make up about a quarter of all registered voters, are cross-pressured," Pew says. "Their attitudes on the social safety net and immigration are somewhat closer to those of Romney supporters, while they tilt closer to Obama supporters in opinions about labor unions and some social issues."