This is a good article about how the media pretends both sides are to blame for partisanship.
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A classic example is a recent Washington Post column by David Broder, a justly-respected reporter and columnist famous for, and much beloved because of, his advocacy of bipartisanship. "The roots of political gridlock in Washington and of the hyper-partisanship dividing "red" and "blue" America," Broder wrote in May, can be seen in the fates of two lawmakers. Sen. Arlen Specter (R-Pa.), a moderate, survived a near-death primary challenge this spring, while Rep. Jack Quinn (R-N.Y.), another veteran moderate, announced his retirement, paving the way for a likely Democratic takeover of his heavily-unionized district. These two races "illustrate how the ideological lines dividing the parties are being etched ever deeper," Broder opined, as if describing some impersonal geologic force. Indeed, Broder connected these two races to a decades-old realignment that "has been so gradual that its effects are often overlooked": the slow fading away of conservative Southern Democrats and liberal Northern Republicans.
Broder is of course right that such a realignment has taken place. But the vast majority of truly right-wing Democrats defected to their natural modern home in the GOP years ago. The interesting question is what's driving the process now. Broder didn't venture a guess, but the answer is implicit in the examples he chose. Quinn is retiring from a party that has treated moderates like him with disdain. Specter was almost bumped off by Rep. Pat Toomey (R-Pa.), a conservative hardliner whose campaign received substantial funding from ideologically-uncompromising right-wing groups such as the Club of Growth.
Nothing remotely like this has occurred on the Democratic side. Sure, a number of moderate-to-conservative Democratic Southerners, such John Breaux (D-La.) and Bob Graham (D-Fla.) are retiring this year. But with the exception of Zell Miller (D-Ga.), none seem to be doing so because of anger at, or pressure from, the liberal wing of their party. Quite the contrary: hand wringing over the loss of moderate Southern Democrats is a party-wide obsession. Indeed, Senate Democrats were so afraid of losing Miller's vote in the Senate that neither his frequent and virulent denunciations of the party leadership nor his decision to endorse Bush for re-election provoked a single public rebuke. (By contrast, when Sen. John McCain (R-Ariz.) last month questioned the wisdom of cutting taxes during wartime, the GOP Speaker of the House, Rep. Dennis Hastert (R-Ill.) questioned whether McCain understood the meaning of sacrifice.) And it's hard to remember the last time a moderate Democratic senator faced an ugly, well-funded primary challenge by a hardcore left-liberal, the way Specter did from his right.
That the Democrats are still pretty congenial to their centrists suggests the degree to which the party has become, if not less partisan, then surely more ideologically moderate. Indeed, the recent Democratic primary in Pennsylvania illustrates the point. To challenge Specter in November, the state's Democratic voters chose Rep. Joe Hoeffel (D-Pa.). A member in good standing of the New Democrat coalition in the House, Hoeffel represents a majority-Republican district and supported, among other things, Bush's No Child Left Behind Act and the Iraq war resolution.
http://www.washingtonmonthly.com/features/2004/0406.glastris.html