Whatever chance Chuck Hagel's detractors had of bringing him down, it appears to be going by the wayside. With just four days until he is expected to be confirmed by the Senate, developments in recent days have the clear feeling of a last hurrah for the anti-Hagel movement.

To wit:

* 15 GOP senators on Thursday sent President Obama a letter urging him to withdraw Hagel's nomination. The letter, which was notably not signed by two-thirds of the GOP Senate caucus nor by Sen. John McCain (R-Ariz.), seemed to be more of a final statement about Hagel's nomination for the record books rather than an actual effort to convince Obama to withdraw him.

* Sen. Richard Shelby (R-Ala.) said he would vote for Hagel, officially giving Hagel the 60 votes he will need to overcome a GOP filibuster. True, Republicans had already said they wouldn't filibuster Hagel anymore starting Tuesday, but Shelby's decision to support Hagel seals the deal. Given there were 59 votes to invoke cloture last week, Shelby makes 60. So even if Republicans for some reason wanted to continue to filibuster Hagel on Tuesday, they couldn't. (Worth noting: Shelby did seem to add a caveat to his support, saying he reserved the right to change his mind if something new came along, but it's logical to assume that would probably be the case for any of the other Republicans supporting Hagel, too.)

* The "Friends of Hamas" situation made the anti-Hagel forces look silly. A story in the conservative media that Hagel may have received donations from a group called "Friends of Hamas" was based on little more than innuendo and, not surprisingly, turned out to be bogus -- so bogus that the group itself doesn't even appear to exist. While there were many legitimate reasons for Republicans to oppose Hagel, this made them seem desperate and gave Hagel advocates something to point to when they argued that the opposition amounted to a witch hunt.

* Similarly, in filibustering his nomination, Republicans suggested there might be some further disclosure that would disqualify Hagel. They have come up snake eyes. There have been second-hand reports about things Hagel said about Israel at a pair of speeches as Rutgers University, but there were no recordings of the speeches and the sourcing was thin. Then a reporter for the conservative Weekly Standard tried to get access to Hagel's yet-to-be-opened archives and was denied, but that story hasn't really caught on either.

At this point, anti-Hagel sources are acknowledging the odds are stacked against them but are still hoping for a last-minute Hail Mary. They're suggesting that they've already succeeded in making an issue of Hagel's past and bringing important issues to the forefront.

"The opposition is historic because the nominee's abhorrent views are historic," said one, who asked for anonymity to discuss the matter frankly.

Republican strategist David Norcross, who called the Hagel nomination a "cynical, political choice" by Obama, acknowledged the opposition hasn't landed a game-changer.

"I don't know that I would say the opposition is crumbling, but it isn't gaining significant traction either," Norcross said. "Odds certainly and unfortunately favor confirmation."

To be clear, it's not surprising that Hagel is very likely to be confirmed -- Republicans acknowledged as much even as they launched their filibuster last week.

But the unspoken purpose of that filibuster was to buy themselves some time to figure out another way to thwart Hagel.

They haven't found it, and the clock is running out.