Fred Thompson, as you may have heard, is currently not a candidate for president. The former Tennessee senator is technically just “testing the waters” and, as he’s wont to say, the waters are pretty warm. However, his coyness could end up costing him — possibly in the neighborhood of seven figures.

A liberal blogger by the comic book-ready name of Lane Hudson has filed a complaint with the Federal Election Commission pointing out the obvious: While Mr. Thompson claims to be evaluating the prospect of running for president, in reality he’s already running. This wouldn’t matter terribly, except that it’s against the law. By perpetrating this sham, he’s abusing a legal status that allows him to conduct certain activities (hiring staff, conducting polling, doing limited fund raising) without the hassle of declaring that he’s a candidate or filing regular reports to the FEC.

For its part, the Fred Thompson for President Exploratory Committee has responded with a simple statement: “We’re following the law.” But of course, saying it doesn’t make it so. The committee will have 15 days to come up with a better answer once the FEC officially notifies it of the complaint. In the meantime, let’s look at the law and the evidence from the complaint.

The strongest case can be made based on a section of the law that states a candidate has ceased to test the waters — and has, instead, jumped in — when “The individual makes or authorizes written or oral statements that refer to him or her as a candidate for a particular office.”

On this point, the campaign (mostly the candidate himself) has been flagrant.

In one case, back in late June, Mr. Thompson was asked when he was going to announce his candidacy. “I have a general time in mind,” he said. “You’re either running or not running. I think the steps we’re taking are pretty obvious.” Nod, nod; wink, wink.

In another instance, in mid-July, a Thompson consultant, Mary Matalin, told the Washington Post, “He has made up his mind” about running and was just waiting for the right time to announce.

In the most recent instance, from just last week, Mr. Thompson told CNN: “We are going to be getting in if we get in, and of course, we are in the testing the waters phase. … We’re going to be making a statement shortly that will cure all of that. But yeah, we’ll be in traditionally when people get in this race.”

There’s also the fact that the Thompson committee has signed a long-term office lease (it’s not supposed to engage in activities “over a protracted period of time”) and that it raised $3.4 million in June, including $72,000 for the general election (it’s not supposed to “amass campaign funds” that would be spent once the candidate has declared).

The other presidential campaigns have been buzzing about this for months. But none has complained publicly — least of all formally to the FEC — for fear of coming off as petty or out to attack Mr. Thompson. Still, an adverse result from the FEC could harm Mr. Thompson and help his opponents.

First off, there’s the hypocrisy factor. Mr. Thompson helped shepherd Senator McCain’s signature McCain-Feingold campaign finance-regulation bill through the Senate. It wouldn’t be good for him to get caught skirting the law.

Second, there’s the possibility of a hefty fine from the FEC. If the FEC finds that Mr. Thompson was in violation of its regulations, it could declare that he failed to report millions of dollars in contributions when he should have. One campaign lawyer not connected to any of the campaigns speculates that if the FEC takes those millions as the base of its calculations, its fine would easily reach six figures and could even top $1 million.

A former commissioner of the FEC and noted opponent of campaign finance regulation, Brad Smith, said this Thompson case “shows the ridiculousness of the whole regime.” What’s really at stake here, he asks, when Mr. Thompson’s donations will all be disclosed once he declares?

But while Mr. Smith is right about the general overregulation of our politics, the blogger who started all this fuss by calling Mr. Thompson out (when Mayor Giuliani, Mitt Romney, Mr. McCain, and others weren’t willing to) has a point, too. “If he can’t follow the law before he’s even a real candidate for president,” Mr. Hudson asked me yesterday on the phone, “then what can we expect from him for the rest of the time?”