HALF NELSON…. Yesterday, Sen. Judd Gregg (R) of New Hampshire announced his support for Elena Kagan’s Supreme Court nomination, bringing the total number of Republicans backing confirmation to five (and counting). For Democrats who might be looking for bipartisan cover, there’s plenty here.

But for Sen. Ben Nelson (D-Neb.), it’s apparently not good enough.

Senator Ben Nelson of Nebraska announced Friday that he will not vote to confirm Elena Kagan to the Supreme Court, becoming the first Democrat to oppose the president’s nominee.

“I have heard concerns from Nebraskans regarding Ms. Kagan, and her lack of a judicial record makes it difficult for me to discount the concerns raised by Nebraskans, or to reach a level of comfort that these concerns are unfounded,” he said in a statement. “Therefore, I will not vote to confirm Ms. Kagan’s nomination.”

But Mr. Nelson said that he would not join Republicans if they attempt a filibuster.

“In my view, this nominee deserves an up or down vote in the Senate.”

Yes, let’s all marvel at Nelson’s graciousness.

This is all rather hard to believe. It seems unlikely Nelson’s office lines have been burning up with anti-Kagan calls, and even if the senator has heard from some constituents on this, he should probably realize that organized right-wing activists aren’t going to vote for him anyway, so there’s no real point trying to impress them.

But note the specific rationale — Nelson’s heard from opponents of the Kagan nomination, which he’s struggled with because of her inexperience as a judge. I’m not even sure what this means, exactly. He would “discount” far-right complaints if Kagan had been a judge? What does one have to do with the other?

For the record, the “lack of a judicial record” canard is still weak.

Kagan’s legal experience is comparable to that of conservative justices, and experts agree that she is qualified for the Supreme Court. The American Bar Association gave Kagan its highest rating: well qualified. Justice Antonin Scalia reportedly said that he was “happy to see that this latest nominee” is “not a judge at all.” Retired Justice Sandra Day O’Connor said it didn’t matter that Kagan had not been a judge. In addition, other legal experts and prominent conservatives reject claims that Kagan isn’t qualified. At least 38 justices — including two of the past four chief justices — had no judicial experience when they were first nominated for the Supreme Court. And Kagan’s legal experience is comparable to that of several recent conservative justices at the time of their nominations: William Rehnquist, Clarence Thomas, and John Roberts.

The Kagan confirmation vote will likely occur on Tuesday. Whether Nelson will switch parties won’t be clear until January.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.