It is to be expected that Sen. Susan Collin, R-Maine, would celebrate the selection of Reince Priebus as chief of staff for Donald Trump. The chairman of the Republican Party, Priebus is just the kind of figure Washington Republicans want in the White House, as a tether between the party and the unpredictable president-elect.

But we should also expect Collins to speak out against Trump’s worst impulses, starting with the appointment of Stephen K. Bannon. Bannon, as the head of Breitbart News, fomented the most hateful and dangerous segments of the far right, and now he has the ear of the most powerful man in the United States.

Stephen Bannon leaves Trump Tower in New York in November. Associated Press/Evan Vucci

We hope Collins, who publicly declared Trump unacceptable during the campaign, will continue to act as a moderating force in a federal government soon to be completely under the control of Republicans. And with Trump’s selection of Bannon, moderating force is desperately needed.

Bannon took over Breitbart News, a conservative, populist opinion and news site, after the death of founder Andrew Breitbart and turned it into the chief mouthpiece and instigator of the so-called “alt-right” – a loose white-nationalist group outside the conservative mainstream.

In addition to run-of-the-mill conservative news dressed up in bombastic headlines, Breitbart trafficks in a mix of rumor, conspiracy theory and innuendo aimed at appealing to the alt-right’s notion of white supremacy. Immigrants and refugees are portrayed as imminent, violent threats, plotting and organizing against Americans. Inner cities are said to be on fire, in utter chaos and on the verge of collapse. Breitbart’s articles have said Muslims were seen celebrating on rooftops on Sept. 11, 2001, and that Islamic terrorists have infiltrated the Obama White House, or Hillary Clinton’s campaign team.

All unsubstantiated, reckless, and extremely popular with Americans whose views have no good place in America. And indeed, until recently, those views were relegated quietly to the fringe.

But now, with Bannon’s appointment, the alt-right is represented in the White House, its views validated at the highest reaches of U.S. power. The racists, misogynists and anti-Semites in its ranks now have a license to more openly act on their backward and hateful views.

There’s plenty to be concerned about in the Trump administration. It is worrisome to think how, say, Newt Gingrich would act as secretary of state, or Rudy Giuliani as attorney general. Trump’s three eldest children are prominently involved in both his White House transition team and his private company, inviting unprecedented conflicts of interest. He reportedly is considering a climate-change denier to head up the EPA, as well as dim lights such as Sarah Palin and Sheriff Joe Arpaio for prominent positions.

But that in a lot of ways is just the politics of a new presidency. Bannon is something more, one of the main reasons why the nation’s racist underbelly now feels so comfortable acting out in the open.

Such a man should not have a place in the Oval Office. With Democrats out of power, it is up to Republicans to say so.

Collins has made herself powerful as a sensible, centrist Republican who can temper the worst inclinations of each party. Her leadership is needed more than ever now.