For months, contenders vying for Louisiana's open U.S. Senate seat largely played nice, at least publicly. But with the Nov. 8 election only three months away, the attacks have started and appear likely to escalate as candidates try to stand out in the 24-person race.

The front-runner, Republican Treasurer John Kennedy, took direct hits this week, mainly from GOP U.S. Rep. Charles Boustany, but also from Democratic candidate Josh Pellerin, an oil and gas businessman.

Meanwhile, Democratic lawyer Caroline Fayard is describing herself as the strongest opponent to white supremacist David Duke, a Republican who jumped into the race only hours before the signup closed. The campaign for the leading Democratic candidate, Public Service Commissioner Foster Campbell, reacted by accusing Fayard of using Duke to seek attention for her candidacy.

The Senate seat is open because Republican David Vitter isn't seeking re-election.

Boustany's campaign has been hammering Kennedy in the last few days, accusing the treasurer of supporting a $1 billion tax hike on the oil and gas industry, one of Louisiana's largest business sectors.

The Lafayette congressman cites a wide-ranging report from the legislative auditor that identified inefficiencies in state government. Kennedy forwarded the report to Gov. John Bel Edwards in February, suggesting it could help shrink state spending. Among the items in the report is an estimate that Louisiana lost more than $1 billion in taxes through a tax break for horizontal drilling of oil and gas wells.

The Boustany campaign says that amounts to Kennedy "advocating a $1.1 billion tax hike on the oil & gas industry at a time when working families in the energy industry are being laid off across the state of Louisiana."

The treasurer said he's never supported doing away with the horizontal drilling tax break and just because he forwarded the report doesn't mean he endorsed every item contained in its pages. Kennedy said anybody who's followed his political talking points for years knows he's repeatedly urged lawmakers and the governor to cut spending, not to raise taxes.

"When you're leading (in polls), people make up stuff about you. It's unfortunate, but it's happened," Kennedy said.

Pellerin also took aim at Kennedy, in a forum and a campaign email. He described the treasurer as a career politician who helped create the state's financial problems during former Gov. Bobby Jindal's tenure. He didn't mention, however, that Kennedy regularly — and publicly — clashed with the Jindal administration over its spending and budgeting tactics.

Since his surprise entrance into the race, former Ku Klux Klan leader David Duke has been criticized by all the major candidates running for Senate. Duke has replied with widespread hits of his own to GOP and Democratic opponents alike.

Fayard is touting her attacks from Duke, making them a centerpiece of her talking points. In a Facebook post, Duke linked Fayard to Democratic presidential candidate Hillary Clinton and called them both "white leftist, extremely wealthy 'melting pot' pushers."

Fayard launched a radio ad this week that declares she is the "only one person in the race who's the direct opposite of David Duke." At a forum, she called Duke's criticism a "badge of honor."

Campbell's campaign says Fayard is seizing on Duke to try to draw attention to a struggling campaign.

"Ms. Fayard is desperately trying to grab free press by escalating a fight with David Duke to cover up the fact that she's been MIA for every fight that has mattered for our people," Campbell spokeswoman Mary-Patricia Wray said in a statement.