U.S. Rep. Marsha Blackburn, the Republican nominee for Tennessee’s open U.S. Senate seat, has twice been on the list of speakers for a conference organized by an anti-Muslim activist group, and has met with leaders of a far-right Austrian political party with Nazi roots.

Blackburn, who has previously faced criticism for her association with a former leader of a neo-Confederate hate group, was listed as one of 20 confirmed speakers — including Milo Yiannoupolous and Steve Bannon — at the November 2017 Restoration Weekend, a three-day gathering hosted by the David Horowitz Freedom Center.

She is also listed as a confirmed speaker on a blog post outlining the agenda for the 2011 conference.

Although listed as an event speaker, a Blackburn aide said she did not attend the 2017 Restoration Conference. The staffer did not say why, or whether she had attended any of the organization's other events.

Spokeswomen for Blackburn last year and on Wednesday said the congressman is appalled by the hate groups and condemns their actions.

The David Horowitz Freedom Center, listed by the Southern Poverty Law Center as an anti-Muslim hate group, says its mission is to confront “the efforts of the radical left and its Islamist allies to destroy American values and disarm this country,” and Horowitz has said that the “only serious race war” is “against whites.”

In January 2017, Blackburn met with members of Austria’s Freedom Party, a far-right political party founded by one-time Nazi officers “whose leaders have continued to engage in anti-Semitism and Holocaust trivialization in recent years,” according to the Anti-Defamation League.

Blackburn is seen posing with members of the Freedom Party in a photo tweeted by U.S. Rep. Steve King, R-Iowa, two nights before President Donald Trump’s inauguration.

King, who has made racist remarks about Muslims and immigrants and who recently retweeted a neo-Nazi, is pictured next to Blackburn in the photo. He hosted the dinner held at the Capitol Hill Club, a Republican social gathering spot where Blackburn spent $652.97 that day, according to campaign finance filings.

Posing with Blackburn and King are Freedom Party leader Heinz-Christian Strache and others from the Austrian political party, including Norbert Hofer, a far-right candidate who unsuccessfully ran for president of Austria in 2016.

Facing criticism from outside groups, Freedom Party officials earlier this year appointed a committee of historians to assess its links to Nazis.

ACT For America, FAIR among other Blackburn conferences

Although Blackburn was only billed as a speaker at the 2017 Restoration Weekend conference, she has also spoken at other gatherings that watchdog groups say promote a hateful ideology.

While Blackburn's campaign didn't respond to a question about whether she had concerns with sentiments on Muslims held by David Horowitz and others associated with his Freedom Center, campaign spokesman Abbi Sigler said that "Marsha condemns any form of hate in the strongest terms."

Blackburn has spoken at and attended multiple conferences hosted by ACT for America — an organization also considered an anti-Muslim hate group by the Southern Poverty Law Center — including one as recently as 2016.

Blackburn spoke at the ACT convention’s legislative briefings each year from 2012 to 2016, receiving an award for her work at the 2014 conference, according to the Anti-Defamation League.

She is among other Republican lawmakers who have spoken at ACT events, including Sen. Ted Cruz of Texas, former U.S. Rep. Mike Pompeo, the current Secretary of State, and U.S. Rep. Lou Barletta of Pennsylvania.

In 2015, Blackburn also attended an annual gathering hosted by the Federation for American Immigration Reform, also known as FAIR, which the SPLC labels an anti-immigrant hate group.

The conference, dubbed "Hold Their Feet to the Fire," draws several dozen talk radio hosts who broadcast interviews with lawmakers, anti-immigration activists and law enforcement officials.

The USA TODAY NETWORK - Tennessee has been unable to locate any video or audio of her speeches at ACT for America or of radio interviews given during a 2015 Hold Their Feet to the Fire conference.

Heidi Beirich, director of the Southern Poverty Law Center's Intelligence Report, said it’s “troubling when elected officials speak to hate groups,” which she describes as endorsing and “providing cover for bigotry.”

Politicians’ engagement with groups like DHFC, ACT for America and FAIR in turn allows them to argue that their views are not extreme, Beirich said.

“You’re allowing a group to put forward views that are really ugly and have no place at this level,” Beirich said. “They should be on the fringes of society, and not connected to mainstream political leaders.”

Blackburn has previously come under fire for her 2004 invitation to a Tennessee pastor and former president of the state chapter of the League of the South, a SPLC-designated neo-Confederate hate group, to lead a prayer on the floor of the U.S. House of Representatives.

The pastor, David O. Jones, had advocated for southern secession.

Last fall, when Talking Points Memo reported on Blackburn’s invitation to Jones, a spokeswoman for the congressman said she was “appalled and saddened by the actions and words of these hate-filled organizations.”

The spokeswoman also noted Blackburn had not seen Jones in more than a decade and was not aware of his affiliation with League of the South. The Confederate group, which was instrumental in organizing a white nationalist rally last October in Shelbyville, said Jones is no longer part of its ranks.