Here's a graph by Andrew Gelman (h/t Paul Krugman) that brilliantly refutes all the nonsense that America is a "center-right nation."

As you can see, House Democrats received over 50% of the two-party vote in every election since 1946 except 1994. And even in the Gingrich Revolution of 1994, Republicans only got 52% of the two-party vote.

House votes are infinitely more useful in looking at national ideology than Presidential votes. The biggest Democratic Presidential vote was LBJ's landslide 1964, which was a fluke resulting from the assassination of JFK. The biggest Republican Presidential vote was Nixon's landslide in 1972 over George McGovern, which was also a fluke.

For the past 62 years, House Democrats have received roughly 55% of the vote, except from 1994-2004. A good case could be made that the force undercutting natural Democratic strength during those years was powerful rightwing talk radio (Rush Limbaugh, etc.) and cable TV (FOX).

The progressive blogosphere (including Democrats.com) grew in response to rightwing radio and TV lies. Those lies became clear to everyone when the U.S. military found no WMD's in Iraq after the 2003 invasion. Bush barely stole the 2004 election by using the power of the White House to keep Americans in fear with regular terror alerts, and by using the power of rightwing radio and TV to convince Americans John Kerry shot himself to get his medals. But the continuing carnage in Iraq gradually turned a majority of Americans against Bush, and Bush's dismal response to Hurricane Katrina finally convinced them Republicans are incapable of governing.

Update 1: The actual point of Gelman's blog is that House Democrats did better in 2008 (56%) than Obama (53%). That makes the idea absurd that Americans want Obama to block Congressional Democrats from enacting a progressive agenda. If Americans didn't want a progressive agenda, they wouldn't have elected a Democratic Congress.