With Beau Biden sidelined, and Charlie Cook forecasting Delaware’s Senate race to be a “solid Republican” pickup, Rep. Mike Castle (R., Del.), the GOP frontrunner, tells National Review Online that he is “feeling pretty good” about his chances. “With or without Beau Biden in this race, I’ve always been positive about my prospects,” he says.

Could Castle’s candidacy help the GOP win back the Senate? “I think that’d be a little bit of a reach,” he says. “However, having said that, I think it’s very likely that we will gain seats in the Senate. We see the trend in Massachusetts. I think we have a good chance of picking up at least five seats.” The House, he adds, “has a better chance” of turning red in 2010. “In both chambers there is going to be a tightening of party ratios. Whether or not they’re in GOP control, a tightening should be enough to cause to the White House to have to deal with Republicans as well as Democrats when making decisions. From health care to the economic debates, we’ve had too much single-party rule in the first year of the Obama administration.”

Castle, a former governor who’s been elected statewide 12 times, says that regardless of which Democrat steps up to face him, he’ll be able to “remind people of the time I was governor, when there was very low unemployment and high-level jobs coming into the state.” Comparing his record to what’s happened under Obama “will almost be devastating,” he says. He’ll also have the money to do it: Castle now has $1.7 million in his campaign war chest following a fundraising surge last quarter.