Right-wing groups that cheered the government shutdown last year and/or have backed a host of questionable GOP challengers this year seem to be scrambling. They can, I suppose, keep “score” any way they please, but in finessing the figures they risk losing even more credibility as the purity testers for the right.

Jim DeMint, president of the Heritage Foundation, gestures during a news conference on immigration reform Monday, May 6, 2013, in Washington. The Heritage Foundation presented a study that immigration legislation would cost taxpayers $6.3 trillion to provide government benefits for millions of people now living in the U.S. illegally. Supporters of the legislation call the study deeply flawed. (AP Photo/Evan Vucci) Jim DeMint, president of the Heritage Foundation, at a news conference in 2013. (Evan Vucci/Associated Press)

Roll Call, for example, reports that both Heritage Action and Club for Growth somehow missed scoring the flood insurance bill in the Senate (they both opposed it in the House), but when questioned/caught went back to retroactively score the bill, thereby having to knock down Texas Republican Sen. Ted Cruz’s perfect score:

Heritage Action Communications Director Dan Holler told CQ Roll Call that the reason the key vote hadn’t showed up online, and the reason Cruz still has a 100 percent score, is that the “hamsters” hadn’t updated the site yet.

“We’ll get the scores up and running sooner than Healthcare.gov is running,” Holler said.

But senators, and GOP leadership for that matter, might be wondering why they weren’t told in advance that the flood insurance bill would be key voted.

“It sounds like Heritage Action got caught trying to cover for some senators,” a senior GOP aide told CQ Roll Call on Friday. “Their conservative principles seem pretty flexible.”

The aide added: “These games are one reason why Heritage’s credibility is in crisis on the Hill.”

Holler noted that Heritage has always reserved the right to “retroactively” key vote, though he said that wasn’t the case in this instance.

Part of the problem may be that the Senate vote to clear the House-passed flood insurance bill came up rather abruptly Thursday after a deal was worked out with several senators that avoided a protracted amendment process. . . . Holler said he couldn’t remember an instance when Heritage had not notified members officially that they were key voting a piece of legislation, but he said, “I’m sure we have at times.”

Holler also said he could “guarantee you folks in the Senate knew where we were on it.”

Indeed, Heritage Action did make their position well known, which is why it seemed all the more puzzling they weren’t including it on their scorecard. Heritage Action insists this is just a technology issue, and that there was nothing nefarious going on with them not notifying senators they were key voting the bill.

That might have been more believable had Club for Growth not also failed to score the bill in the Senate. After being questioned, CFG also — wouldn’t you know it? — “will likely score the vote retroactively, noting that they key voted against the legislation in the House.”

Heritage Action, of course, began to permanently damage its credibility with House Republicans when it move the goal posts on the farm bill.

Again, these groups can score bills however they like, but the latest incident points out how utterly arbitrary the process can be. Why not score votes for and again Iran sanctions, for example? Why give credit for show votes on the shutdown? (CFG ducked the immigration reform issue entirely.)

There are other ways to rig the system. FreedomWorks and Senate Conservatives Fund have gotten blasted for spending millions to back laughable Senate candidates like Matt Bevin in Kentucky and Milton Wolf in Kansas. What to do? Well, fill up the scorecard with safe bets so the big mistakes don’t stick out.

Hence, FreedomWorks just announced it would back a slew of GOP incumbents (whose voting records are not materially different from Republican senators Pat Roberts and Mitch McConnell), including Sen. Jim Inhofe of Oklahoma, Sen. Tim Scott of South Carolina and Jim Risch in Idaho, none of whom have significant opposition.

The Senate Conservatives Fund has even started endorsing House members, which may help even out its win-loss record. That said, it will be hard to convince donors and conservatives more generally that these maneuvers make up for disastrous, expensive support for flaky challengers. (As I’ve noted before, CFG has tried to stick to a more reasonable approach when it comes to endorsements.)

None of this would matter very much if these groups did not set themselves up as the arbiters of conservatism. Unfortunately, too many groups have made their reputations and plenty of money accusing fellow conservatives of selling out. That charge tends to fall flat when your strategic advice flops, your candidates bomb and your vote scoring proves to be awfully arbitrary.