In a letter to the U.S. Department of Justice last week, two campaign finance watchdog groups pressed for an investigation of a “dark money” organization and its role in the White House run of U.S. Sen. Marco Rubio, R-Fla.

The groups said it sure looks as if Conservative Solutions Project, a nonprofit set up as a social welfare organization under federal tax laws, isn’t doing much else than trying to get Rubio elected president: The nonprofit has spent more than $5 million in states deciding early in the Republican nomination process for TV advertisements that feature Rubio in discussions of policy issues.

Paul S. Ryan, of the Campaign Legal Center, one of the two watchdog groups, said it appears Conservative Solutions Project is violating two regulations: a ban on spending by social welfare organizations to aid any one candidate and a requirement that the organizations devote more than half of their activity to benefiting the general public.

The legal center focused on the pro-Rubio group because of the amount of money involved and because of Rubio’s emergence as a major contender for the nomination, spokesman David Vance said.

“There are so many laws being broken right now that we have a laundry list of potential complaints,” he said.

One possible entry for that list, Ryan said, would be America Next, the dark-money group boosting a less prominent candidate for the Republican presidential nomination: Gov. Bobby Jindal.

Ryan emphasized that he has not investigated America Next. But in discussing America Next’s activities, he said, “It seems to exist for the purpose of promoting Bobby Jindal as a candidate” — which would be “impermissible.”

America Next was organized in 2014, months before Jindal officially declared his candidacy in June this year. Its website has published proposals on health care, national defense and other issues written by Jindal, who is listed as the group’s chairman.

America Next has spent about $350,000 producing commercials supporting Jindal, according to its federal filings. The home page for its website prominently displays a 30-second video of clips from Jindal’s campaign speeches with his name splashed on the screen.

America Next has ties to OnMessage, the Washington-area consulting firm that handles Jindal’s political advertising. America Next’s 2014 IRS filing lists its chairman as Rolfe McCollister Jr., a longtime Jindal associate; McCollister was the treasurer in January for the formation of Believe Again, the independent political action committee dedicated to Jindal’s election. America Next’s executive director, Jill Neunaber, also serves as a senior adviser to Believe Again.

Brad Todd, of OnMessage, who helps coordinate outside spending for Jindal, said America Next operates within the law. Social welfare groups “can most certainly engage in independent express advocacy, provided that activity is not the group’s primary purpose and the advocacy is consistent with, and promotes, the group’s social welfare purpose,” he wrote in response to an emailed request for comment sent to him and Neunaber.

The TV ads, aired last summer, touted the group’s position on a strong national defense and highlighted Jindal’s support as consistent with that, he wrote.

In July, Todd included the $4 million raised by America Next in his calculation of the more than $9 million backing Jindal’s White House push. Believe Again, a second pro-Jindal outside group called American Future Project and Jindal’s official campaign committee all filed required federal reports that month detailing contributions received and expenditures.

But America Next did not file, because it didn’t have to. As a social welfare organization, it need submit only reports summarizing its income and listing expenditures. It does not have to disclose the identities of its donors.

That’s why America Next, and the Conservative Solutions Project backing Rubio, are called dark-money groups. And it’s their lack of disclosure that is particularly troubling to campaign finance reformers.

The Campaign Legal Center isn’t optimistic that the IRS will enforce the rules on the organizations to which the agency grants social welfare status. Worried about abuse of the rules, several Democratic senators in 2012 pushed for tighter regulation of the groups. But the resulting attempted crackdown was at best clumsy and at worst malicious, and it blew up in 2013 into the IRS targeting scandal. One predictable effect is the chilling of any additional effort by the agency.

So the complaint about the Conservation Solutions Project was directed to the Justice Department, not the IRS, Ryan said.

“The DOJ is really our last hope in the federal government,” he said.

Gregory Roberts is chief of The Advocate Washington bureau. His email address is groberts@the advocate.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.