The only surprising aspect to President Donald Trump's racially charged tirade this week is that some seemed surprised by it.

"Yet again this president finds a new low," said Sen. Tina Smith of Minnesota, a home state colleague to Rep. Ilhan Omar, the prime target of Trump's invective.

But for a president who has shattered nearly every conventional rule of politics and endured a cascade of uproars – from his birther campaign to insulting a national war hero to the "Access Hollywood" tape to the two-year wide-reaching investigation into his curious relationship with Russia – Trump has been taught that survival requires brazen, line-crossing, double-fisted pugilism.

"It's playing the game," Trump told confidantes, according to Michael Wolfe's latest book, "Siege: Trump Under Fire." "I'm good at the game. Maybe I'm the best. … Most people are afraid that the worst might happen. But it doesn't, unless you're stupid. And I'm not stupid."

The worst hasn't happened to Trump.

Yet.

But if he's not stupid, he can easily read the writing on the wall. His approval rating rarely budges 45 percent and 2020 general election polls consistently show him losing to Joe Biden and Sen. Bernie Sanders of Vermont, with other Democrats steadily improving their standing against the incumbent.

"Whoever the nominee is, they're just the surrogate for the squad. The squad is the Democratic Party."

There's a flurry of reasons two dozen Democrats joined this presidential race. One is that Trump looks beatable. A loss in 2020 would render him an American aberration, a temporary, if not insignificant blip in the country's long arc of history. But a victory would mean ultimate validation of Trumpism and likely spur a horde of Trumpian replicates who would employ the same bitterly divisive and xenophobic tactics.

By the data, Trump stands as an underdog going into his reelection – just like he was against Hillary Clinton in 2016. And placing all the caveats about flawed polling and a hidden Trump vote aside, this president is already telegraphing running the same type of raucous, no-holds-barred insurgent-style campaign that continues to outrage the masses and force his opponents to consider new lows.

Instead of "Lock her up!" the signature chant he regularly invoked against Clinton, parts of a Greenville, North Carolina, crowd on Wednesday night began shouts of "Send her back!" as Trump ticked through a list of the Somali-born Omar's more controversial statements about the Sept. 11 attacks and al-Qaida.

On Thursday, Trump said he wasn't happy with the chant, the first time in four days he had sought to deescalate the increasingly hazardous rhetoric. But it was his Sunday tweets, telling the freshman female Democratic "squad" – Reps. Alexandria Ocasio-Cortez of New York, Rashida Tlaib of Michigan, Ayanna Pressley of Massachusetts and Omar – to "go back where they came from" that culminated in the raucous rally that even some Trump allies found uncomfortable.

"I didn't like last night's 'send her home' chant," says Bryan Lanza, the deputy communications director for Trump's 2016 campaign. But Lanza says it's fair game to target the freshman four – not due to their race or gender – but because its their ideology that is defining the Democratic Party.

Photos: Trump and His Supporters View All 72 Images

"Let's be honest. There's a Democratic primary called the AOC primary. Elizabeth Warren is trying to suck up to her. Kamala Harris is trying to suck up to her. Even Joe Biden is trying to suck up to AOC. Of course you're going to talk about the squad when they are running to seek their endorsements. Whoever the nominee is, they're just the surrogate for the squad. The squad is the Democratic Party."

The squad is burdened with its own share of extreme and polarizing rhetoric. Ocasio-Cortez has called the immigration detention facilities on the southern border "concentration camps." Omar vaguely referred to the Sept. 11 attacks as "some people did something." Tlaib has associated with anti-Israeli activists, including at least one who has praised Palestinian terrorism.

In many ways, they present Trump a much more enviable foe than the crop of Democrats running to defeat him. But if he can tie the more extreme aspects of the squad to the eventual nominee – who could very well be a woman, or even a woman of color herself – he could enhance his own viability as the safer choice.

It's divide and conquer through fear and loathing in the defense of unabashed nationalism.

Given the strength of the economy, Trump could powerfully run on a singular message of growth and prosperity in peacetime.

But his impulse is to scratch the country's darker underbelly of tribalism that's fomented by racial and religious differences. It folds neatly into his obsessions with resurrecting a wall for border security and administering tariffs in international trade.

Still, advocating for protecting the border is very different than pleading with elected representatives to self-deport themselves across it.

In what may be a somewhat surprisingly statistic to Beltway elites, 51 percent of voters said they support raids by Immigration and Customs Enforcement officers, according to a Morning Consult survey. Yet more than two-thirds of voters told USA Today they believe Trump's tweets telling the Democratic congresswomen to go back to the countries "from which they came" are offensive.

Some Democrats doubt that Trump will be able to get away with the fear-mongering any longer, and they point to 2018 midterms as their evidence.

"We honestly think Trump made a mistake," says Matt Bennett, co-founder of the centrist Third Way group. "This narrowed the map even further, because those suburban voters who crushed the Republicans in 2018 do not like this kind of thing."

But if anything has been learned from 2016, it's that Trump's ultimate opponent will matter most.

"The D next to the names of every Democrat on the ballot will be defined by the nominee and no one else," Bennett says. "Not by [Nancy] Pelosi, not by a freshman member of Congress, not by Trump. By our nominee. So we had damn well better get that right."

