On Sunday, President-elect Donald Trump announced two additions to his incoming administration: Reince Priebus as his chief of staff and Steve Bannon as his chief strategist and senior counselor.

While Priebus has been in the public eye as the Republican National Committee chairman, Bannon, 62, worked behind the scenes as Trump's presidential campaign CEO. Although the chief of staff has historically been the gatekeeper to the president, Bannon got top billing on the press release.

Top Democrats in Congress and prominent anti-defamation groups decry Bannon's appointment and point to his rhetoric and leading role with Breitbart News as indications that he holds white nationalist and anti-Semitic views.

Bannon became the executive chairman of the website after the death of its founder, Andrew Breitbart, in 2012. Critics say Bannon used his position to promote the alternative right, or alt-right, movement, which the Southern Poverty Law Center describes as a "set of far-right ideologies, groups and individuals whose core belief is that white identity is under attack by multicultural forces using political correctness and social justice to undermine white people and their civilization."

Under Bannon's leadership, Breitbart has published articles with such headlines as "Bill Kristol: Republican Spoiler, Renegade Jew," "Birth Control Makes Women Unattractive and Crazy" and "There's No Hiring Bias Against Women in Tech, They Just Suck at Interviews."

In an interview with ABC News' "Powerhouse Politics" podcast, a former Breitbart spokesman, Kurt Bardella, described conference calls with Bannon as similar to "attending a white supremacist rally" and accused him of having nationalist ideals and "hatred for immigrants."

Bardella was one of a few staffers who left Breitbart in March after its handling of allegations by Michelle Fields, a reporter for the site at the time, that then–Trump campaign manager Corey Lewandowski assaulted her.

In a Buzzfeed report, some Breitbart employees accused the site of having a financial agreement with Trump to publish positive coverage of his campaign.

Members of Trump's team defended Bannon today against the accusations.

"Well, look, first of all, I don't know where they are coming from. This is not the Steve Bannon I know," Priebus said in an interview on "Good Morning America." "I have sat with him for months, and I have never ever experienced that, and I think these people are taking it way too far."

Kellyanne Conway, Trump's campaign manager, who was hired at the same time as Bannon, argued that people "should look at the full resume."

Bannon said that the alt-right appeal to racists was happenstance.

"Look, are there some people that are white nationalists that are attracted to some of the philosophies of the alt-right? Maybe," he told Mother Jones. "Are there some people that are anti-Semitic that are attracted? Maybe. Right? Maybe some people are attracted to the alt-right that are homophobes, right? But that's just like there are certain elements of the progressive left and the hard left that attract certain elements."

Bannon has had a variety of careers, including serving in the Navy. In the 1980s, he worked for Goldman Sachs. In the 1990s he started an investment bank working with media companies. Before joining the Trump campaign, he resided mostly in Los Angeles, and this decade he switched focus to making conservative films. In 2011 he made the movie "The Undefeated," about Sarah Palin, which first got him notice with the tea party movement and Andrew Breitbart.

According to a Politico report published in April, Bannon was charged with misdemeanor domestic violence and battery in 1996. He pleaded not guilty, and the charges were dropped because of a lack of witnesses. In the complaint obtained by Politico, his then-wife said he "pulled at her neck and wrist" and smashed the phone when she tried to call the police after a dispute over money.

A spokeswoman for Bannon told ABC News that he has a great relationship with his ex-wife and their children.

Regardless of those controversies, Bannon will continue to have a direct ear to the president-elect as chief strategist and senior counselor.

ABC's Katherine Faulders and Meghan Keneally contributed to this report.