In Washington, there's a saying: You can judge a politician by his or her staff.

On Sunday, President-elect Donald Trump gave us a lot to chew over with regard to that.

He announced that his chief of staff will be the the zero-controversy choice of Reince Priebus. Priebus is head of the Republican National Committee, a buddy of House Speaker Paul D. Ryan's (they're both from Wisconsin) and, crucially, a Republican who refused to give up on Trump when others did.

But on Sunday, Trump also appointed the very controversial Steve Bannon as one of his top aides. And Trump is getting A LOT of heat for that. To explain why, let's explain who Bannon is:

He's the former head of Breitbart News: That's the hard-right conservative blog that has been a thorn in establishment Republicans' side and a pro-Trump megaphone throughout this campaign.

Steve Bannon (Carlo Allegri/Reuters)

Under Bannon's leadership, Breitbart evolved as an outlet for the alt-right to write controversial things about immigration, terrorism and racial issues. The nonpartisan civil rights organization Southern Poverty Law Center had this to say about Bannon:

Here's more controversial headlines that ran on Breitbart under Bannon:

He's been working with Trump since August: When Trump's campaign floundered this summer, Trump decided to name Bannon to a top role in his campaign.

Bannon's ascension could "weaponize" Breitbart to hold the GOP to the right: So says conservative talk radio host Charlie Sykes (a Trump critic) in an interview with The Fix's Callum Borchers.

BORCHERS: "Could Breitbart's news coverage impact the way Republican politicians run for office, to the point where they say, 'We need to embrace or at least pander to the Breitbart audience or they will kill us'?"

SYKES: "Yes, I think that's a very real possibility. This is part of the culture: 'If you break with us, we will unleash the flying monkey against you' — Breitbart being the flying monkey."

Controversy alert: Trump's children

President-elect Donald Trump's wife,  Melania Trump, left, daughter Ivanka Trump, and sons Eric Trump and Donald Trump Jr. (Tasos Katopodis/AFP/Getty Images)

While he's president, Trump is going to hand over control of his business to his adult children -- the aim being to avoid any financial conflict he might run into while president. But most watchdog experts say that's not nearly enough distance between the leader of the free world and his bank account.