Republican U.S. presidential candidate Donald Trump. (Joshua Roberts/Reuters)

Jonathan A. Greenblatt is the chief executive of the Anti-Defamation League

Donald Trump’s recent tweet of an anti-Semitic image has been roundly criticized by commentators, public officials and journalists of all political stripes. The malevolent origins of the graphic have been established, but some have debated why it was tweeted at all: Was it simply an errant tweet? Did the Trump campaign make an innocent mistake, using the image without checking its source? Did the campaign’s fact-checkers simply fail at their job? Or, as Trump said Wednesday night, did the campaign not see anything wrong with it at all?

These questions miss the point.

The Trump campaign, with its regular use of anti-immigrant, anti-Mexican and anti-Muslim rhetoric, has appealed to bigots and racists. It has attracted an odd menagerie of anti-Semites, white supremacists and haters with a disturbing penchant for slandering and swarming critics online and offline. In particular, journalists — who simply have reported on Trump and his family — have been viciously targeted. The bigots who perpetrate these attacks typically invoke white nationalism and the Trump campaign as they promote their hateful ideology.

The fact that these individuals have used the Trump phenomenon to spread their bigotry is not a thing of Trump’s own creation; these racists and anti-Semites existed before Trump announced his candidacy. But the campaign’s repeated flirtation with these elements — retweeting their content and quoting their heroes — has helped to mainstream their ideas.

This is not speculation. Former KKK grand wizard David Duke publicly endorsed Trump and has celebrated his campaign. Neo-Nazi Andrew Anglin has thanked Trump for sending signals. And there is a wide range of white supremacists and other racists who espouse his greatness on extremist discussion boards and social platforms.

At a time when hate crimes have galvanized the nation and when it has appeared that old barriers and hatreds have been fading into memory, it is both shocking and deeply troubling to see a national figure mainstream intolerance and hate. As we mourn the recent loss of Nobel laureate Elie Wiesel, we should not be quibbling over a clear instance of anti-Semitism. Indeed, this mainstreaming of hate threatens to undermine the social progress of the postwar era.

We see it at political rallies where members of the media are viciously harassed and minority protesters are attacked. We hear about it from parents who report that their Muslim or Latino children are taunted on the playground for who they are and told that they will be sent back “home.” And it appears in the statistics. In the Anti-Defamation League’s recently released annual “Audit of Anti-Semitic Incidents,” we found an increase over the prior year — and a doubling in the number of anti-Semitic assaults. We certainly cannot state that these are the result of campaign rhetoric, but these statistics are worrying, to say the least.

How do we stop this hatred and harassment? It starts with leadership.

Candidates seeking election to the presidency should be the first to condemn hatred, racism and anti-Semitism wherever and whenever they appear. They should marginalize it and never allow it to seep into the mainstream.

This is why we find it outrageous that Trump, his staff and his supporters, rather than accepting responsibility for circulating an anti-Semitic meme, instead have tried to deflect blame by claiming that the media contrived the story or suggesting that it was a “sheriff’s star” or even dismissing any criticism of it as little more than “political correctness.”

It’s long past time for Trump to take three simple steps: acknowledge his errors, apologize for them and unequivocally reject the hate-filled extremists orbiting around his campaign. Trump needs to make clear that he doesn’t want their voices lending their support or their votes in November. Simply put, he should say loud and clear, again and again, that he has zero tolerance for anti-Semitism, racism and hate, and the people who espouse these ideas have nothing to do with his agenda or his campaign.

Opposing hate isn’t a liberal or conservative issue. It’s an American issue. And while our organization takes no position on who should be our next president, the ADL is firmly committed to calling out bigotry and prejudice wherever we see it and whoever may say it.

As the general election campaign approaches, I hope that our fellow Jewish communal groups and civil rights organizations will join us in speaking out against intolerance and hate. We must not write this off as “politics as usual” because it isn’t. We must make our voices heard and use our collective power to condemn anyone who traffics in this bigotry. Doing that is the only way we can show them and the world what really makes America great.