After the 2006 midterm elections, victorious Democrats stressed that their win was a move back to the center and that the 110th Congress would see an influx of moderate Democrats. At the time, I was a skeptic, noting that many moderate Republicans were swept out and that many of the newly elected Democrats would turn out to be more liberal than they seemed. But initial evidence of congressional voting patterns does show that, at least in the House, a surprising number of freshman Democrats are voting on the conservative side of their party.

Over the past 50 years, the once-prevalent conservative Democrats and liberal Republicans have disappeared, leaving a much more polarized party system.

The 2006 elections continued this trend towards fewer moderates — at least on the Republican side of the ledger. Nine of the 20 most moderate Republicans lost, according to the vote ratings of political scientists Keith Poole and Howard Rosenthal (Voteview.com), with many losses occurring in Northeastern and Midwestern districts that John Kerry had won in 2004.

But what of the Democrats who replaced Republicans? Are they voting as moderates? Using Voteview rankings for the first six months of 2007, none of the 30 Democrats who replaced Republicans are among the most liberal 20 percent of Congress, although David Loebsack (D-Iowa) almost falls into that category. Twelve of the 30 are in the second most liberal quintile. But 18 of the 30 can be categorized as moderates, falling into the middle quintile of Congress.

Looking at the numbers in a different way, eight moderate Republicans were replaced by liberal Democrats. For example, moderates Nancy Johnson (R-Conn.) and Rob Simmons (R-Conn.) were replaced by more liberal Chris Murphy (D) and Joe Courtney (D). Five moderate Democrats replaced moderate Republicans, an example being Ron Klein (D-Fla.) replacing Clay Shaw (R). Four districts that were once represented by conservative Republicans, like Richard Pombo (R-Calif.) now have liberal Democrats, like Jerry McNerney (D). But most strikingly, 13 conservative Republicans were replaced by moderate Democrats. Among the biggest changes, J.D. Hayworth (R-Ariz.) and Chris Chocola (R-Ind.), who had voting records among the 10 percent most conservative, have been replaced by Harry Mitchell (D) and Joe Donnelly (D), respectively, who rank almost exactly in the middle of the 110th Congress.

The Senate is a different story. The most conservative new Democrat is Jon Tester (D-Mont.), who is clearly in the moderate category, ranking as the 44th most liberal senator, and he replaced conservative Conrad Burns (R). In two cases, liberal Democrats replaced conservative Republicans. George Allen (R-Va.) was replaced by Jim Webb (D).

Webb is not as liberal as Allen was conservative, but Webb fell just outside the moderate category. And in the biggest shift, conservative Rick Santorum (R-Pa.) was replaced by a liberal, Bob Casey Jr. (D). The characterization of Casey as liberal may surprise some because of his salient pro-life stance, but on the overall plate of issues, he is tied for the 10th most liberal senator. In one case, a moderate Republican, Jim Talent (R-Mo.), was replaced by a moderate Democrat, Claire McCaskill (D). Overall, however, moderates suffered, as two Republican moderates, Lincoln Chafee (R-R.I.) and Mike DeWine (R-Ohio) were replaced by much more liberal Democrats Sheldon Whitehouse and Sherrod Brown, who rank as the fourth and 14th most liberal senators, respectively.

The bottom line is that in the House, the exit of many Republican moderates has been more than made up for by new moderate Democrats. In the Senate, moderates saw a loss of one. Good to know that moderates are not extinct.

Fortier is a research fellow at the American Enterprise Institute.