WASHINGTON — “From the start,” Hillary Clinton said in a speech on Thursday, “Donald Trump has built his campaign on prejudice and paranoia,” making her strongest case to date on how Trump is encouraging an emerging extremist movement associated with white nationalism.

At a rally in Reno, Nevada, Democrat Clinton took aim at Trump and what is called the “alt-right.”

You’ll be hearing more about the alt-right in the context of Trump’s Republican candidacy. Don’t blame yourself if you haven’t heard about the alt-right until now. Trump’s presidential run – and his choice for a new campaign CEO, and now Clinton’s speech — are shining a spotlight on an underbelly of U.S. politics.

The Southern Poverty Law Center, which researches and tracks hate groups, defines the alt-right this way:

“The Alternative Right, commonly known as the Alt-Right, is 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. Characterized by heavy use of social media and online memes, Alt-Righters eschew ‘establishment’ conservatism, skew young, and embrace white ethno-nationalism as a fundamental value.”

It’s not a surprise that Trump is, as the SPLC put it, a “hero” to the alt-right.

Trump planted the seeds of his presidential candidacy by taking a leading role in promoting “birtherism,” encouraging the lie that President Barack Obama was not born in the U.S., a way to try to delegitimize the election of the nation’s first black president.

In a recent staff shakeup, Steve Bannon, a Breitbart News executive, was installed as the new Trump campaign CEO. The Breitbart site is an outlet for stories appealing to the alt-right. Trump also added an experienced, savvy GOP pollster, Kellyanne Conway, as his campaign manager.

With the new campaign leadership, in the past few days, Trump has done some outreach to Hispanics and African-Americans. Along those lines, he also started calling Clinton a bigot.

Trump’s visit to Chicago last March, just before the Illinois primary, is being recast by Trump surrogates as a campaign stop aimed at minority outreach. That’s not true.

A Trump spokeswoman, Katrina Pierson, repeated that wrong assertion about Trump’s Chicago visit on CNN on Thursday. On the Friday before the Tuesday Illinois primary, Trump canceled a rally at the University of Illinois at Chicago when skirmishes broke out between his supporters and protesters.

I reported last May that the only reason the rally was at UIC, according to Kenneth Gray, a Trump staffer who booked the venue, was because no suburban locations were available. The United Center wanted $80,000 a night and the UIC charged only $10,000 in rent, not counting other costs for police and extra staffing.

For the record: There’s a lot of justifiable criticism of Clinton when it comes to her State Department emails. She should have distanced herself from Clinton Foundation donors when she was secretary of State.

For the record: Hillary Clinton is not a bigot. That’s not right.

By the way: Trump left Chicago having done no pre-primary event – for minorities or anybody else. Clinton spent the day before the Illinois primary meeting with Hispanics, and later, African-American families of victims of violence.

I see these race-based moves more as Trump and his team trying to appeal to persuadable swing voters who are aghast at a string of Trump’s race-based slams at Muslims, Mexicans and others. His record is his record.

“Trump is reinforcing harmful stereotypes and offering a dog whistle to his most hateful supporters. It’s a disturbing preview of what kind of president he’d be,” Clinton said Thursday.

“And that’s what I want to make clear today: A man with a long history of racial discrimination, who traffics in dark conspiracy theories drawn from the pages of supermarket tabloids and the far, dark reaches of the internet, should never run our government or command our military. Ask yourself, if he doesn’t respect all Americans, how can he serve all Americans?

“Now, I know that some people still want to give Trump the benefit of the doubt. They hope that he will eventually reinvent himself – that there’s a kinder, gentler, more responsible Donald Trump waiting in the wings somewhere.

“Because after all, it’s hard to believe anyone — let alone a nominee for president — could really believe all the things he says.

Said Clinton, “But here’s the hard truth, there is no other Donald Trump.”