The successful prosecution of Tyler Harber may not quite equate to a shot across the bow of the ocean liner of campaign finance, but it could cause a flicker of reflection on the part of political operatives — and provide a ray of hope, however faint, to advocates of more vigorous enforcement of federal regulations.

Harber pleaded guilty in federal court in Virginia this month to illegally coordinating the activities of a congressional candidate’s campaign with a super PAC, a type of political action committee exempt from limits on contributions it receives because its spending — on advertising and other political activity — is supposed to function independently of any campaign.

The Harber case stands out because such prosecutions are extremely rare — less, campaign-finance reformers say, because the political players are so well-behaved than because the federal authorities are dozing at the switch.

The Harber case was “low-hanging fruit,” said Paul S. Ryan, of the watchdog Campaign Legal Center in Washington. Nonetheless, Ryan said, “It’s a good sign that the Department of Justice prosecuted this obvious violation of the coordination rules.”

What’s troubling to Ryan is that some apparently obvious examples of coordination aren’t violations at all. Candidates aren’t supposed to ask super PAC donors to give more than the $5,000 limit that applies to other PACs — but it’s perfectly OK for a candidate to make his pitch at a fundraiser and then turn the microphone over to an operative who asks for bigger checks.

Super PACs frequently are operated by close associates of candidates and may be explicitly dedicated to a single candidate’s election. Such is the case with Believe Again, formed early this year with an announced goal of putting Gov. Bobby Jindal in the White House. Its treasurer is Rolfe McCollister, who was finance director for Jindal’s 2007 gubernatorial campaign and was appointed by Jindal to the LSU Board of Supervisors. He’s also the treasurer of another Believe Again PAC, a nonsuper version set up in 2014 as a Jindal vehicle.

But Jindal is not yet an announced candidate for the 2016 Republican presidential nomination: He has said he is thinking and praying about the decision and will make up his mind in the next month or two. So he does not have to worry about the coordination rules now, as he has no official campaign committee to not coordinate the super PAC with.

That’s also true for the rest of the potential presidential contenders, none of whom has formally announced. But that excuse has its limits.

Federal election law addresses something known as “testing the waters,” defined as activities undertaken “for the purpose of determining whether an individual should become a candidate.”

Even if the “individual” has not announced a run for office, those activities can be paid for only with money contributed under the rules governing official campaign committees. Those rules bar contributions by corporations or unions and cap individual donations at $2,700. So money contributed under the looser regulations governing super PACs and the other type of PAC Jindal (and others) have set up could not be spent to test the waters, nor could contributions to a nonprofit “social welfare” organization like the Jindal-affiliated America Next.

Under federal guidelines, testing the waters can include paying staffers, making phone calls or taking trips for the purpose of determining whether to run. The Believe Again super PAC is too new to have filed a spending report with the FEC; the other Jindal-connected PAC spent about $265,000 in 2014, including on contributions to candidates for Congress, administrative travel, campaign strategizing and mailings, phone calls and other fundraising expenses; and America Next doesn’t have to file an FEC report.

Not surprisingly, none of the potential candidates has admitted to testing the waters — not even Wisconsin Gov. Scott Walker, a Republican who recently opened an office in Iowa, site of the first nominating event (the Iowa caucuses in February 2016).

In an email, Jindal’s key political adviser, Timmy Teepell, denied that Jindal was doing anything in the way of determining whether to run in his frequent travels to Iowa, New Hampshire (site of the first 2016 presidential primary) or other venues to give speeches and participate in panel discussions.

Jindal’s purpose, Teepell wrote, is to support Republican candidates, to argue for Republican ideas and conservative solutions, and to oppose failed liberal policies.

Gregory Roberts is chief of The Advocate Washington bureau. His email address is groberts@theadvocate.com, and he is on Twitter, @GregRobertsDC. For more coverage of national government and politics, follow The Advocate Politics Blog at http://blogs.theadvocate.com/politicsblog.