In the fiercely competitive North Carolina Senate Republican primary, frontrunner Thom Tillis was quick to pounce on his opponent Greg Brannon last month for paying his property tax late this year.

Brannon did not pay his annual property tax on his primary residence until February, nearly six months late, when a reporter alerted him to it being unpaid — and Tillis' campaign responded by sending out a mailer attacking Brannon for his tardiness.

“Senate candidate Greg Brannon has failed to pay his own taxes,” the mailer read. “How can he be a voice for North Carolina taxpayers?”

“We felt that it was important to point out what is basically a matter of public record on his property taxes,” Jordan Shaw, Tillis’ campaign manager and spokesman, told the Charlotte News & Observer at the time, explaining the attack.

But Tillis can hardly boast of a spotless record himself.

For the past five years, Tillis has consistently been tardy paying annual property taxes on his home in Cornelius, N.C., public records show.

Because Tillis paid his taxes after the due date but before the date at which the tax begins to accrue interest, the payments were considered late but not delinquent.

"There's a reason there's a grace period," Shaw told the Washington Examiner.

Shaw said the payments were "all postmarked within the same calendar year" of the due date, although they were at least four months late.

"I think there's a difference between being within the grace period and not," Shaw said, when asked if Tillis' late payments could be compared to Brannon's.

For Brannon, property tax tardiness is also a much deeper problem than previously reported — but only in some cases have his late payments been delinquent enough to accrue interest.

Since 2009, Brannon received late fees during two years for county property taxes on his primary residence in Cary, N.C. — including this year, in the incident that has fueled Tillis' attacks.

Brannon also was hit with late fees on property taxes during three of the past five years for his beach house in Supply, N.C. Like Tillis, Brannon has paid his other property taxes during the government's grace period after the official due date. Brannon's campaign declined to comment.

Brannon and Tillis are two candidates vying for the GOP nomination for Senate in North Carolina. Voters will head to the polls Tuesday, but it's not clear whether Tillis, the frontrunner, will win the 40 percent necessary to avoid a run-off election. Brannon has been placing second to Tillis in most polls, often followed by Mark Harris, a baptist pastor.

Brannon will get a boost Monday from Sen. Rand Paul, R-Ky., at a campaign event in Charlotte. Meanwhile, Mitt Romney announced Monday that he is throwing his support behind Tillis, who was endorsed last week by former Florida Gov. Jeb Bush, a potential 2016 presidential hopeful.