Rep. Mike Castle (R-DE-At Large) announced yesterday that he will retire from the House to seek the remaining four years in vice-president Joe Biden’s Senate term. If you look at Castle’s Progressive Punch numbers, he has a lifetime score of 261, which places him as the fifth-most moderate Republican in the House of Representatives (behind Joseph Cao of Louisiana, Dave Reichert of Washington, and Chris Smith and Leonard Lance of New Jersey). Rep. Mark Kirk (R-IL) has also announced that he is retiring to seek an open Senate seat. In his case, it is for a full six-year term in President Obama’s old seat. Kirk’s Progressive Punch score is 269, making him the thirteenth-most moderate Republican in the House. Are you seeing a pattern?

Up in New Hampshire, the Democrats are trying to paint former Republican Attorney General Kelly Ayotte as the second-coming of Sarah Palin, but it looks more like she is going to campaign in the middle,

Ayotte, who served both Republican and Democratic governors as attorney general, declined to say in a recent interview with the New Hampshire Union-Leader how she voted in the last two gubernatorial races. “I worked very hard to make sure that politics didn’t come into [the attorney general’s office], even though people knew publicly I was a Republican,” she told the newspaper. “I don’t think it would be fair now to revisit each candidate I voted for or supported because it would politicize the time I spent in the office.”

During the interview, Ayotte also sought to straddle several political wedge issues, including abortion rights (she’s pro-life but wouldn’t say whether Roe v. Wade should be overturned) and the recent Supreme Court nomination of Sonia Sotomayor, whom Ayotte said she’d have voted to confirm even though “I didn’t agree with all of her decisions.”

The Republicans’ preferred candidate to succeed Mel Martinez in Florida is the moderate governor Charlie Crist, who famously endorsed Obama’s stimulus package, causing outrage in the GOP’s base.

Former E-Bay executive Meg Whitman is a Republican candidate for governor in California, despite giving her endorsement and a $4,000 check to Senator Barbara Boxer’s 2004 reelection campaign. While former Hewlett-Packard executive Carly Fiorina, the preferred candidate to take on Boxer in 2010, is hardly known as a movement conservative.

In Ohio, former U.S. Trade Representative and director of Bush’s Office of Management and Budget, Rob Portman is the likely GOP nominee to replace retiring moderate George Voinovich. Portman, like Voinovich, is more of a Wall Street Republican than a bomb thrower.

The Republican base is not thrilled with these candidates. And they will be waging spirited primaries against most of them. But it’s clear that the powers-that-be in the Republican Party aren’t taking their cues from the teabagging brigade. If the GOP has a big election night in November 2010, we could see a reduction in the Democrats’ 60-vote caucus in the Senate. But, the most likely result of that will be a restoration, of sorts, of a rump of moderation in the Republican Party.

Before we get there, however, the Republican Establishment has to first carry these relative moderates to victory in their primaries. And, even if the Republicans succeed in picking off seats in places like Delaware, Illinois, and California with moderate candidates, those candidates will probably behave no better than Snowe, Collins, and Specter behaved during Bush’s presidency. They, along with candidates like Crist, Portman, and Ayotte, would make true bipartisanship possible again in the Senate, but I wouldn’t count on them being even a modest improvement over the alternatives. If the Democrats can pick up two or three or four more Senate seats, getting 60 votes for cloture will become a lot easier.