Some Republican conservatives are batting around a "purity test," a way to separate which candidates deserve to have the National Republican Committee give its endorsement and money to them and which candidates do not.
Mike Castle cannot past the test.
Never mind that he is the Republicans' Number One candidate for the U.S. Senate around the country, the prospect regarded as most likely to break the Democrats' 60-vote, filibuster-proof stranglehold on the chamber.
Not to mention the gloating the Republicans could do if Castle commandeered the seat that used to belong to Joe Biden, especially if he beats the vice president's son who is expected to be the Democrats' candidate.
The purity test has 10 parts to it: less government and taxes, no Obama-care; no cap-and-trade bill on pollution; secret ballots on union elections; no amnesty for illegal immigrants; troop surges in Iraq and Afghanistan; no nukes for Iran and North Korea; no gay marriage; no government-funded abortion; and no government restrictions on gun ownership.
Castle figures he is good for six of them. The other four are debatable. He did not spell out which was which.
"It reminds me of being in school. Can I pass this or not?" Castle quipped.
Not unless he gets extra credit for an unbroken streak of nine terms as Delaware's lone congressman, two as governor and one as lieutenant governor, and not unless he does not lose points for other departures from the conservative perspective.
There was that unforgettable moment, for instance, that Castle became the first member of Congress to have a bill vetoed by the second George Bush for advancing embryonic stem cell research, a conservative taboo.
It was another of those middle-of-the-road things. How un-Republican to get the first veto, while there were who knows how many Democrats who would have been delighted with it. Something else Castle denied them.
Six out of 10 may not get Castle much on a conservative purity test, but it does make him the political Goldilocks of Delaware. Not too left, not too right, just enough to get him six or seven out of every 10 voters election after election.
The purity test has touched off enough of a backlash that it is expected to crumble next month at the Republican National Committee's winter meeting in Hawaii.
Delaware's members -- state Chair Tom Ross, National Committeewoman Priscilla Rakestraw and National Committeeman Laird Stabler -- plan to attend with the intent of blocking it.
"Purity, it's a little ridiculous. As Republicans, we're all about local control," Ross said.
The purity test, even with its anticipated demise, is a reminder of the hazards out there for moderate Republicans like Castle within their own ranks.
There were consequences as recently as last month in the off-year election. The Republicans lost an upstate New York congressional district that was theirs for about a century and a half, when outside conservative forces like Sarah Palin and the Club for Growth swarmed in and undercut the Republican nominee by championing a conservative alternative.
There is more to come. The Club for Growth is stirring up a Senate primary in Florida against Charlie Crist, the Republican governor who is trying to live down a hug he gave Barack Obama.
Castle looks fine at home. The state party leadership certainly is with him, and he also has a formidable ally in Pete du Pont, who was the governor when Castle was the lieutenant governor. Not only does du Pont have Castle's back, more importantly he has Castle's right flank.
As governor from 1977 to 1985, du Pont was a pragmatist, but he moved right to run for president in 1988 and has been influential in conservative circles since. He predicted Castle would be left alone.
"I don't think there's going to be a primary. He's just exactly the right candidate," du Pont said.
Thus spake Pete du Pont. It matters.
"I don't think Pete du Pont, who chose Mike Castle as his lieutenant governor and brought him to prominence, is going to stand idly by and let Club for Growth spike Mike Castle," said Rakestraw, the national committeewoman.
A threat from the Club for Growth has crossed Castle's mind but not spooked him.
"You always have these thoughts. I have not made it a contingency part of planning for our campaign. I trust them to make the decision not to come in," Castle said.
Castle is no favorite of the Club for Growth. In its congressional rankings, Castle comes in at #172, so low it is where the Democrats start showing up. In fact, a couple of Democrats are ranked higher than he is.
Nevertheless, the Club for Growth appears to be staying away, even if it is doing so with all of the enthusiasm of Cornwallis surrendering to George Washington at Yorktown.
"He's definitely not the sort of candidate we would back. Frankly, he's the sort of candidate we would think about opposing, but we haven't seen a viable alternative. The race really isn't on our radar screen right now," said Mike Connolly, the communications director for the Club for Growth.
Castle is more focused on where he stands with another club, one that also has a lot of conservatives in it.
"As far as I know, I'm supported by all Republican senators. The alternative of having a moderate Republican or a Democrat is clear," Castle said.
As the saying goes, the only vote in the Senate that really counts is for majority leader, and the Republicans there want Castle's. Purity pales before politics.