— A national report tying millions of dollars in National Rifle Association political spending to a major campaign vendor for U.S. Sen. Thom Tillis has opened more questions of illegal coordination in the rough-and-tumble 2014 Senate race.

The Campaign Legal Center in Washington, D.C., filed a Federal Election Commission complaint in the matter Monday. This is the second time this year the group has reached back to Tillis' 2014 election and suggested illegal coordination by outside groups.

Brad Todd, a founding partner for OnMessage, a key vendor for the Tillis campaign, denied any wrongdoing Monday in a statement to WRAL News, blasting an article Politico Magazine published Friday as a liberal hit piece.

That article was written by a journalist for The Trace, which is funded in part by Everytown for Gun Safety, a gun-control effort bankrolled by former New York City Mayor Michael Bloomberg. Politico published the article in partnership with The Trace, which works with a number of news publications. The piece is based largely on state and federal campaign finance records, reviewed by election attorneys, and OnMessage declined to comment for it.

The story lays out connections between OnMessage and Starboard Strategic, which gets nearly all of its business from the NRA. They have the same address and leadership, and Starboard Strategic appears to have been created in 2013 to handle millions of dollars in NRA political ads.

At the same time, OnMessage did millions of dollars in business with the Tillis campaign and other candidates.

Federal election rules prohibit coordination between candidate committees and the outside groups that finance so-called issue ads, which often appear to the public as thinly veiled efforts to elect or defeat particular candidates. In part, this is to keep those outside groups from getting around maximum contribution limits to candidate committees. The limits don't apply to the groups that finance issue ads.

Federal rules allow consulting firms to take on candidate clients as well as outside groups active in the same race, but they require firewalls between the efforts to prevent illegal coordination. Todd said in an email Monday that OnMessage and Starboard Strategic have such firewalls in place "and follow campaign finance laws meticulously."

"The entire thesis of the column is false," he said in the email.

The records The Trace relied on are undisputed, editorial director James Burnett said.

"Those records raise clear questions about Starboard, OnMessage and the NRA," Burnett said. "Maybe the firms will be more forthcoming with regulators than they were with us."

Todd declined to give WRAL News details on the firewall, including the names of Starboard Strategic employees who worked on NRA ads in 2014 and the names of OnMessage employees who worked on the Tillis campaign. Todd and other company officials didn't respond to detailed questions sent for the Politico article. The NRA and the Tillis campaign declined comment as well.

Paul Shumaker, a lead consultant for Tillis and a mainstay in North Carolina Republican politics, told WRAL News on Monday that he hadn't heard of Starboard Strategic. He said it's standard procedure for companies like OnMessage to have firewalls in place and handle multiple clients and that the article is just an effort to kick up dust ahead of Tillis' re-election campaign in 2020.

"This is about a bunch of political jockeying," he said.

Tillis' campaign manager in 2014, Jordan Shaw, now works for OnMessage. He referred questions Monday to Todd.

The 2014 race between Tillis and then-U.S. Sen. Kay Hagan was the most expensive Senate race in history at the time, coming in around $100 million.

With revelations that Russian operatives may have worked through the NRA to help President Donald Trump get elected in 2016, something suggested by a Senate Judiciary Committee report in May and again Monday when the U.S. Department of Justice unsealed a criminal complaint against a Russian national accused of infiltrating the gun-rights group, the NRA's political spending is under new scrutiny.

Tillis and fellow North Carolina Republican U.S. Sen. Richard Burr have been two of the two top three members of Congress to benefit from NRA political spending in recent years. North Carolina's status as a swing state brings massive amounts of money and advertising from a number of outside groups.

The Campaign Legal Center filed its complaint against the National Rifle Association, citing the Politico piece. This group, headed by a Republican attorney who is also a former chairman of the Federal Election Commission, filed a separate complaint earlier this year accusing National Security Advisor John Bolton's super-PAC of making illegal contributions either to the North Carolina Republican Party or the Tillis campaign by coordinating through a mutual vendor during the 2014 race.

That vendor was Cambridge Analytica, the now-bankrupt British firm at the center of wider accusations that it misused Facebook data to build personality profiles of American voters and that it sent foreign nationals to North Carolina and other states to embed with American political campaigns.

The Bolton super-PAC has denied the accusations against it. The Tillis campaign has said the British advisers didn't make decisions for the campaign, which would also violate FEC regulations.

Tillis' 2014 election also sparked concerns of outside coordination immediately after his win.

Dallas Woodhouse, now executive director of the North Carolina Republican Party, ran a $4.7 million effort called Carolina Rising during that cycle. The group was, in the words of two FEC commissioners "a shadow campaign for Tillis," though Woodhouse maintained the group was running educational ads, not campaign ads.

The night of Tillis' victory, Woodhouse appeared on television saying, "We did it," which led two Democrats on the FEC to call for an investigation. The commission's Republican members declined.

The FEC can have up to six members, but no more than three from any political party. It takes four votes to investigate complaints, which critics say renders the commission useless in enforcing federal campaign finance laws.

Also in 2014, Shaw emailed campaign supporters a detailed memo laying out the campaign's advertising strategy for the final weeks of the race and noting holes left in that strategy. Some saw it as a wish list made public so outside groups could see it.

Anti-coordination rules these days are "almost a fiction," according to Marshall Hurley, an elections law attorney in Greensboro and a former general counsel for the state Republican Party. Hurley reviewed the Politico piece Monday and said "it doesn't look right," referring to the activities described in the story.

Hurley didn't blame the Tillis campaign, saying campaigns have to trust their vendors to follow the rules, such as they are.

"Until people decide that we want some enforcement behind these rules, we're going to be in this gray area," he said.

Update: This story has been updated to include comment from The Trace's editorial director.