Connecticut's junior senator wasn't the only congressional moderate named Joe to lose his primary election last week. Rep. Joe Schwarz (R) of Michigan also went down in a stiff challenge from within his own party – in this case, from the right.
And now another moderate senator – Lincoln Chafee (R) of Rhode Island – is fighting for his political life. If he survives the well-funded challenge of a conservative in his Sept. 12 primary, he faces another tough fight in the general election.
In an election year marked by strong anti-incumbent feeling and the potential for significant Republican losses, many of Congress's moderates – those willing to buck their party leadership at times – are vulnerable. In the House, the potential loss of Republican moderates could intensify the chamber's partisan polarization, adding to the challenges of George W. Bush's final two years as president.
"If Democrats defeat moderate Republicans, it will have the mirror effect of 1994, where you had Republicans defeating moderate Democrats," says Gary Jacobson, a political scientist at the University of California, San Diego. "That boosts polarization, no question."
The long-developing trend toward homogeneous congressional districts – those where partisan preference in presidential elections matches the partisan preference for member of Congress – may become even more pronounced with the vote Nov. 7.
Regional "purity" could also be enhanced. Just as the Southern Democrat has become nearly extinct, so, too, could the "Rockefeller Republican," named for Nelson Rockefeller, former governor of New York and a liberal Republican. The Northeast, home to one-third of the most vulnerable House Republicans, could lose many longtime members.