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(CNN) "You can't step into the same river twice," goes a saying attributed to the early Greek philosopher Heraclitus. Last week's tweetstorm by President Donald Trump raised a related question: Can you descend the same escalator twice?

In June, 2015, Trump rode down to the lobby of Trump Tower and accused Mexico of sending rapists over the border. His incendiary comments helped draw attention to a longshot campaign. Last week, he tweeted about four Democratic women in Congress, three of whom were born in the US: "why don't they go back and help fix the totally broken and crime infested places from which they came." He followed up at his North Carolina rally Wednesday night with criticism of Rep. Ilhan Omar, who came to the US as a teenager, and then paused as the crowd chanted, "Send her back," in an echo of the "Lock her up" chants from his 2016 rallies. (He disavowed the chant Thursday.)

Trump's tweets ledto observe that, "although there has always been a segment that does not trust outsiders -- and bigots who consider non-whites inferior -- most Americans are not racists, not bigots, and not nativists . So why is Trump...betting his re-election on dividing Americans and turning them against their better instincts? He thinks it worked the first time. But this is not 2016." Ghitis argued that as the threat from ISIS and the memory of the Great Recession fades, Americans are less likely to vote out of fear of the other.

"'Send her back' perfectly encapsulates the Trump era, his ambitions and his supporters' zeal for punishing and otherizing his detractors," wrote. "It covers all the features of the Trump doctrine: an appeal to basest instincts, personal animus, racism, xenophobia, revenge. All packed succinctly into three words ." It's not a recipe for long-term success, Cupp noted: "History is a wise judge of character. This will age poorly."

"The 'go back' assault is fundamentally racist and cruel ," wrote. "It's more the language you expect to hear being hurled during the commission of a hate crime, not by the President of the United States. It is a way to harass not just immigrants but any nonwhite person in America." She contended that with their social media savvy, strong base of support among young voters and smart responses to Trump, the four Democrats known as "the Squad" are well positioned to help defeat Trump.

A political trap?

James Pinkerton wrote, in the American Conservative, " Yetwrote, in the American Conservative, " Did Trump just lure the Democrats into a political trap? ...Trump might not be playing chess, but he does have wily ways. He seems to intuit that he would rather be fighting Congress than the eventual Democratic nominee. After all, that nominee could be as moderate as Joe Biden, or as prosecutorial as Kamala Harris, or as new-generational as Pete Buttigieg. Which is to say, the ultimate nominee could be a strong challenger."

Scott Jennings: "The Democratic presidential primary has already seen most of the candidates adopt Squad-approved positions that will The Squad is a gift to Trump, wrote: "The Democratic presidential primary has already seen most of the candidates adopt Squad-approved positions that will cost their party in next year's general election . President Trump and his supporters would be smart to can the weak-minded 'send her back' and change it to 'let her speak.' We can win a contest of ideas; we don't need to get ugly to do it, either."

Moustafa Bayoumi, who wrote in the Guardian, "So now we know what the 2020 election will look like. The contrast is clear to, who wrote in the Guardian, "So now we know what the 2020 election will look like. It will be 'the Squad' versus the mob . On one side is thoughtful and engaged criticism coupled with a progressive legislative agenda. On the other side is a dangerous throng spewing cheap insults, racist taunts and explicit threats."

Karthick Ramakrishnan, a professor at the University of California, Riverside, was the editor of his school newspaper in the early 1990s, when the Persian Gulf war and the Rodney King beating led him to write some pieces critical of US foreign and domestic policy. , a professor at the University of California, Riverside, was the editor of his school newspaper in the early 1990s, when the Persian Gulf war and the Rodney King beating led him to write some pieces critical of US foreign and domestic policy. "Go back to your country" and "love it or leave it" were the taunts he heard in his small town in central Massachusetts. Today the stakes are higher, with those taunts coming from the White House: "This moment is not simply a political food fight between the President and his critics. The claims being made go to the core of what it means to be American. And it is up to us, individually as well as collectively, to steer ...away from the sirens of false patriotism and to uphold the principles of inclusion that have consistently made our country great."

A star tree

Kate Maltby: "When people from minority groups ask Hollywood to think a bit more carefully about who portrays them, they're asking to be treated like human beings -- asking for recognition that their stories are human stories. Scarlett Johansson drew criticism after a magazine interview quoted her as saying, "You know, as an actor I should be allowed to play any person, or any tree, or any animal because that is my job and the requirements of my job." The actress then said her comments had been taken out of context but the outrage over them was understandable, wrote: "When people from minority groups ask Hollywood to think a bit more carefully about who portrays them, they're asking to be treated like human beings -- asking for recognition that their stories are human stories. No one has ever stopped Scarlett Johansson from playing a tree -- whereas they have objected to her playing a trans man or a Japanese woman. The difference between the two is basic humanity."

Maltby added though that Johansson has a point. Acting is about imagination and pretending to be another. "To insist that we only represent our own stories is to deny the fundamental importance of empathy," she wrote. "Johansson's real mistake was to use the word 'allowed.' The problem in Hollywood isn't who's allowed to play each role, but who gets the opportunity."

A Jedi Master

Appointed by a Republican president, John Paul Stevens stood out as a leading liberal voice on a US Supreme Court that moved to the right over his 35 years as a justice. The bow-tied Chicago Cubs fan squeezed a lot of life out of his 99 years, as Richard Lazarus recalled after his death this week. Stevens threw a strike when he threw out the first ball at a Cubs game in his late 80s and swam in open water every day into his 90s.

He was fearsome on the bench: "Unfailingly polite at oral argument, he would invariably begin his questions by asking permission of the advocate to ask a question. But no matter how politely poised, his questions were invariably dagger-like , aimed right at the central weakness of the lawyer's argument. Many of the nation's best lawyers saw their entire cases unravel in seconds after receiving a Stevens question at argument."

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A giant leap

Don Lincoln was a kindergartener who instantly decided he wanted to become an astronaut. He wound up on a different trajectory. Now a senior scientist at the Fermi National Accelerator Laboratory and science educator, Lincoln wrote, " When Neil Armstrong took his first steps on the moon 50 years ago,was a kindergartener who instantly decided he wanted to become an astronaut. He wound up on a different trajectory. Now a senior scientist at the Fermi National Accelerator Laboratory and science educator, Lincoln wrote, " I fully expected that by the time I was an adult, we'd have long conquered Mars and would be on to greater challenges, perhaps even having turned our eyes to the stars." Frustratingly, progress toward interstellar travel has been a lot slower in the decades since Apollo 11. But he retains hope there "will be a day in the future when my great, great, many-times-great, grandchild sits cross-legged with her kindergarten class and sees an intrepid pioneer standing on a planet around a distant sun."

John Avlon, let's not mythologize the era: "One year after the assassinations of Martin Luther King and Robert F. Kennedy Jr., murders were at an all-time high -- more per capita than the current rate. When we look back at 1969, wrote, let's not mythologize the era: "One year after the assassinations of Martin Luther King and Robert F. Kennedy Jr., murders were at an all-time high -- more per capita than the current rate. American cities suffered devastating riots and fires between 1968 and 1969 that led to urban blight and a belief that our cities were in permanent decline. Not only were streets burning but bombs were going off at a frequency we can't imagine today."

Commentators then, as many do today, said America was hopelessly divided, and yet it was a society capable of the epochal achievement of going to the moon.

A life-saving drug

Alyssa Milano. "As a result, as many as one in four people who take insulin skip doses because they cannot afford the medication that is keeping them alive. In response, advocates across the country are mobilizing and fighting back: The prices of widely used forms of insulin have tripled over the past decade, endangering the health of many people with diabetes, wrote. "As a result, as many as one in four people who take insulin skip doses because they cannot afford the medication that is keeping them alive. In response, advocates across the country are mobilizing and fighting back: we're telling patients' stories, we're amplifying each other's voices and we're demanding affordable insulin now ... We cannot afford one more death from insulin rationing."

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It's OK to laugh at the end