There was talk early on of something like a 55 senator advantage in the senate. A couple tea party losses do not account for the current imbalance. A whole lot of candidates, including more than a few establishment picks, failed.
An 8-seat gain (which is all that was needed to get to 55) was not an unrealistic expectation. After all, many were the Dems carried over in the anti-Bush 6th year backlash of ‘06, some occupying heavily GOP seats. It was simply inexcusable that we not only didn’t make gains, but lost seats.
I don’t know what is the problem with Senate contests. Since after 1980 (when we beat 9 incumbent Dems), we have never been able to defeat more than 2 Senate Dem incumbents in a cycle. Two. The Dems almost do that against our side routinely without breaking a sweat. Not even in 1994, the great vaunted GOP year, did we knock off more than 2 (Harris Wofford in PA by Rick Santorum and Majority Leader-presumptive Jim Sasser by Bill Frist in my state of TN). Had it not been for all the retirements producing open seats that year, we’d have likely failed to win the Senate.