Aaron David Miller makes the case  that the anti-Hagel campaign is ultimately just an anti-Obama campaign:
That’s why I think that the Hagel affair really isn’t about Chuck Hagel.
This is really a fight about Barack Obama. It is being driven by three somewhat overlapping constituencies — a pro-Israel community that doesn’t trust the president, a Republican party and a neoconservative elite struggling unsuccessfully to define its own foreign policy identity, and finally, a party in opposition that is determined to remind Obama that, reelected or not, he doesn’t have a free hand.
On one level, Miller is correct. Strident opposition to a presidential nominee is opposition to the president, and many of Hagel’s critics insist on interpreting the selection as confirmation of views that they have frequently and wrongly attributed to Obama. Republican hawks have been railing against a fantasy Obama record for four years, so I suppose it’s inevitable that they would subject one of his Cabinet nominees to the same treatment. Hard-liners convinced that Obama wants to preside over American decline look at Hagel, impute views to Hagel that he doesn’t have, and then say, “Yes, just as we thought, Obama wants to preside over decline.” “Pro-Israel” hawks in the GOP have been pushing the idea that Obama doesn’t support Israel enough since before he was elected, so naturally they will claim that Obama is “revealing” his “real” views by associating him with the distortions of Hagel’s record they are circulating. One nonsensical criticism informs the other.
It’s also true that Hagel is encountering resistance from his own party because Obama appointed him, but it’s equally true that Hagel would never have been given a Cabinet post in a McCain or Romney administration. It’s easy to imagine that a Republican-appointed Hagel would face just as much hostility from the same critics, but it’s very difficult to imagine that a Republican would appoint him to a comparable position in the first place (in part because of the sway Hagel’s critics still have inside the party). Yes, Hagel’s critics are going after Hagel in large part to inflict damage on Obama, but they would not have thrown such a fit over the other possible nominees for Defense, and they have shown no interest in targeting Kerry despite the fact that he will be the one carrying out Obama’s foreign policy. There’s no getting around the fact that this controversy is primarily one about Hagel.
The anti-Hagel campaign is partly a case of sour grapes over losing the election, but it’s also being done as payback to strike at Hagel for his past criticisms of Republican hawks. Hagel’s critics believed that his nomination would make it easier to split off Democrats in the Senate and hand Obama an early setback, but something close to the opposite has occurred. As Pat Buchanan observed  in his new column, the Hagel nomination set up Republican hawks for a no-win scenario:
If Hagel is confirmed, Republican resistance will have been routed. If Hagel is rejected, the Republican Party will be damaged in the eyes of many for having trashed a patriot, war hero and friend of veterans who put America first and wanted no more unnecessary wars.
The problem for Republican hawks in this case is that they didn’t understand that there was no way for them to win this contest, and so they launched their assault on Hagel anyway.