Such rhetoric and actions have provided tacit approval to fringe elements who are considering violence, Trump's critics said. "The numerous statements he's made, calling himself a 'nationalist,' crowds at his rallies chanting threats against George Soros - it's all connected," said Cecilia Wang, deputy director of the American Civil Liberties Union.
White House aides have rejected such accusations. Trump said the mail-bombing suspect should be prosecuted and punished to the fullest extent of the law, and he called the mass shooting in Pittsburgh a "wicked act of mass murder".
Since early in his 2016 campaign, when he denounced immigrants from Mexico as criminals and rapists, Trump has employed language that appeals to the nativist impulses of the electorate - to the point that he was endorsed by former Ku Klux Klan leader David Duke. In his closing ad during his presidential run, Trump warned darkly of a triumvirate of prominent Jews - Soros, Goldman Sachs CEO Lloyd Blankfein and Fed Chair Janet Yellen, and suggested Hillary Clinton was partnering with them in bad faith in a bid to control the global power structure.
Last year, Trump drew far-reaching condemnation for suggesting, in the aftermath of a white supremacist rally in Charlottesville, Virginia, during which a counterprotester was killed, that there were "good people on both sides". Chants of "lock her up" about Clinton and other prominent Democrats and "build the wall" to keep out immigrants have been a staple of his campaign rallies.
Trump has taken action against the caravan of Central American migrant families in Mexico. The Trump Administration authorised sending 1000 military troops to assist in border security operations. The President has suggested, without offering evidence, that criminals and Middle Eastern terrorists are among the migrants.
He and other Republicans floated a conspiracy theory that Soros helped fund the caravan. House Majority Leader Kevin McCarthy tweeted last week that Republicans were under threat of losing in November because of financial support for Democrats from Soros, environmentalist Tom Steyer and New York businessman Michael Bloomberg. "We cannot allow Soros, Steyer and Bloomberg to BUY the election!" McCarthy wrote. "Get out and vote Republican #MAGA." He deleted the tweet after authorities said Soros had been targeted in the mail bomb plot.
"For the Republican Party to deny their stoking of these kinds of sentiments is not believable," said Simon Rosenberg, the founder of NDN, a liberal think-tank. "We know that in the US and Europe right now, there is a rise in right-wing nationalism and political parties are seeing the fuel of their rise be the fear of immigrants and people not like them - classic xenophobia. Trump is mimicking all of the same."
McCarthy denounced the "heinous" attack on the synagogue. Speaker Paul Ryan called the attacks anti-Semitic, an ideology he said must be eradicated, and he vowed that the nation "will not tolerate this bigotry".
Trump has shown no inclination of toning down the rhetoric. He told reporters on Saturday that, if anything, he should "tone it up".
Republican commentator Charlie Sykes, a Trump critic, suggested that the President's focus is misguided. "So, America," he tweeted, "perhaps the greatest danger we face is not a caravan [1600km] away. Maybe it's already here."
