Donald Trump’s dark vision of America polarized political reactions on Friday as Democrats warned against underestimating the power of his convention night appeal to the nation’s fears.  Related: Donald Trump: the madman in his castle  In a speech to formally accept the Republican party nomination, the man portrayed by one speaker in Cleveland as the “blue-collar billionaire” repositioned himself as “the law and order candidate”, the only one capable of restoring safety to a country he claimed was facing existential challenges.  “Our convention occurs at a moment of crisis for our nation. The attacks on our police, and the terrorism in our cities, threaten our very way of life. Any politician who does not grasp this danger is not fit to lead our country,” he said to rapturous applause.  He also claimed to speak for ordinary Americans with an uncompromising reprisal of campaign promises on protectionism and immigration aimed at communities he said were “crushed by our horrible and unfair trade deals. These are the forgotten men and women of our country,” he told a packed crowd that repeatedly broke into chants of “U-S-A, U-S-A” and “build a wall!”. “People who work hard but no longer have a voice. I am your voice,” he claimed.  Related: Fact checking Trump's Republican convention speech: what was true?  It was a message that went down extremely well with Trump supporters, many of whom had been concerned by a chaotic convention that saw Michelle Obama plagiarized by Melania Trump and her husband tacitly rebuked in a speech by former rival Ted Cruz.  As soon as 120,000 red, white and blue balloons started floating down from the roof of Cleveland’s Quicken Loans Arena roof to mark the end of the final speech, delegates on the floor were buried waist deep as they thrashed about in kaleidoscopic celebrations.  Al Baldasaro, a New Hampshire state representative who supported Trump since he launched the campaign, was euphoric. “It feels awesome,” said Baldasaro. “We worked our butts off. Donald Trump is the real deal. The people spoke and we’re there. Now on to Hillary and we’re taking the Hill.” He exited with his wife in a neon Trump hat as the soundtrack changed to the Rolling Stones’ You Can’t Always Get You What You Want.  Yet the 75-minute address, evoking for some the fear mongering nationalism of Richard Nixon rather than Ronald Reagan’s “It’s morning in America” message, caused consternation among moderate Republicans.  A former White House communications director for George W Bush decried themes of “protectionism, isolationism, and nativism” that many fear will alienate independent voters in November’s election.  “The Republican party that I worked for for two decades died in this room tonight,” Nicolle Wallace told NBC.  “The party I was part of is dead,” agreed John McCain’s daughter and Fox News Host, Meghan McCain.  Ed Cox, the chair of the New York State Republican party and Nixon’s son-in-law noted some similarities, told the Guardian: “Certainly Donald Trump calls his supporters the silent majority unapologetically. Now that was not a part of his acceptance speech in ’68, that was November ’69, the Vietnam speech. But Donald Trump has captured that silent majority completely for the first time since Reagan, and maybe even better than Reagan. But certainly like my father-in-law.”  More extreme figures on the right seized on the unprecedented use of nationalist rhetoric as vindication for long-buried but darker impulses of their own.  “Great Trump Speech, America First! Stop Wars! Defeat the Corrupt elites! Protect our Borders!, Fair Trade! Couldn’t have said it better!” tweeted former Ku Klux Klan Grand Wizard David Duke as he announced he was running for US Senate in Louisiana on a ticket to protect “European Americans”.  Trump’s daughter Ivanka insisted her father was “color blind and gender neutral” in a warm-up speech that sought to soften the campaign’s appeal to women, black and Latino voters.  Others debunked his use of crime statistics, particularly claims that the police murder rate had soared, that depended on a selective use of annual comparison periods. Instead the average number of police murders per year has fallen from 101 under Ronald Reagan, 90 under George HW Bush, 81 under Bill Clinton, 72 under George W Bush, to just 62 under Obama.  Fact checkers also noted exaggerated descriptions of the threat to ordinary citizens, particularly when Trump departed from prepared remarks to claim Americans were living through a “more dangerous environment than I have ever seen or anyone has ever seen”.  In early responses from the White House, Barack Obama said that Trump overstated the violence but noted that a recent uptick in homicide rates in big US cities is real, and demands to be addressed. Obama added: “We’re not going to make good decisions based on fears that don’t have a basis in fact, and that, I think, is something I hope all Americans pay attention to.”  Bookmakers showed a small uptick in the odds of Trump winning the presidency after a week of powerful convention headlines, putting his chance of winning the White House at around 30%.  During the convention, Thomas Barrack, a friend and business associate of the New York property developer, argued that one of Trump’s greatest strengths was his ability to manipulate people he did business with. “He played me like a Steinway piano,” said Barrack.  It was a character trait acknowledged by Trump himself during his speech, who said his business experience gave him the skills to fix a rigged country. “Nobody knows the system better than me,” he shrugged with smirk. “Which is why I alone can fix it.”  His former ghostwriter Tom Schwartz responded on Twitter: “This is the Donald Trump i came to know. not a word about hope. not a word about possibility. all doom all the time.”  Democrats also expressed alarm that the polished showbiz performance of Trump, who, for once, rarely strayed from his prepared message and softened controversial language on Muslims, could resonate among a distracted and fearful electorate.  “We have 109 days to stop Donald Trump, so pitch in whatever you can to help make sure we beat Trump/Pence and the rest of the GOP on Election Day,” said a swiftly-issued fundraising email from the Hillary Clinton campaign.  Former Obama campaign manager Jim Messina added, in a tweet: “I woke up today & thought ‘there is no fucking way we can let Trump become POTUS’. Let’s go to work.”  The sharpest reactions however came from outside politics, including those alarmed at what they see as creeping fascism in a speech that mentioned violence and killing nine times each.  US comedian Jon Stewart blasted: “This country isn’t yours. You don’t own it … You don’t own patriotism.”  “I’ve heard this sort of speech a lot in the last 15 years and trust me, it doesn’t sound any better in Russian,” said Vladimir Putin critic and chess grandmaster Gary Kasparov.
Donald Trump’s acceptance speech in Cleveland played upon the nation’s fears, leading some Republican to call it the death of the party