WASHINGTON (Reuters) - Republican Congresswoman Martha McSally accused her opponent in the hotly contested U.S. Senate race in Arizona, Democratic U.S. Representative Kyrsten Sinema, of “being OK with treason” as the two faced off in their only debate.

McSally has increasingly focused on Sinema’s past as an antiwar protester and progressive activist to get an edge ahead of the Nov. 6 elections.

Most recent opinion polls have shown the Democrat with a slight edge in the race for the seat held by retiring U.S. Senator Jeff Flake, a prominent Republican critic of President Donald Trump.

Democrats see it as an opportunity to pick up one of the two additional seats they need for a Senate majority that could allow them to more effectively counter Trump’s agenda.

McSally waited until late in Monday’s debate to cite an interview Sinema gave in 2003, when a local radio host posited a hypothetical question about a person deciding to join the Taliban. Sinema responded: “Fine, I don’t care if you want to do that. Go ahead.”

McSally, a former Air Force fighter pilot, accused Sinema of saying “it’s OK to commit treason.”

The radio interview was first reported by CNN.

Sinema did not directly address McSally’s allegation but charged that McSally had resorted to “smearing” her campaign.

“She’s just trying to cut, cut, cut and not share the full picture,” Sinema said. “The truth is that I’ve always fought for Arizona.”

Sinema’s campaign said McSally brought up the subject to distract from issues such as healthcare. “Congresswoman McSally crossed the line with that desperate attack,” said campaign spokeswoman Helen Hare.

The National Republican Senatorial Committee criticized Sinema on Tuesday for refusing to apologize for the Taliban comments.

Sinema’s politics have changed since she was first elected in 2013. She joined a moderate Democratic coalition and has one of the more conservative voting records among Democrats in the U.S. House of Representatives.

That has not kept McSally from bringing up Sinema’s liberal past as she tries to galvanize Trump supporters in a state he won in 2016.

In an email to supporters on Tuesday, McSally warned the “fake news” media were twisting her words. On Friday, Trump will hold a rally for McSally in Mesa, Arizona.

Last month, the Republican president accused a member of his administration who wrote an anonymous opinion article in the New York Times of “treason.”