This story was originally published in the December 13 edition of CNN's Meanwhile in America, the daily email about US politics for global readers. Sign up here to receive it every weekday morning.

(CNN) Americans: Watch the next few hours in the UK closely.

If the Labour Party's election night goes as disastrously as early exit polls foretell, the Democratic Party may see a cautionary tale for the US 2020 presidential race.

Labour's Jeremy Corbyn took his party way to the left, leaving the more moderate ground where many voters feel most comfortable, including some in his own party and outside. He promised revolutionary change, a fundamental overhaul of society, heavy new taxes on the rich and a far bigger role for the state in the economy. Sound familiar?

Debate has rocked the Democratic Party over whether candidates like Bernie Sanders and Elizabeth Warren are trekking too far to the left and leaving moderates behind. Both are promising an assault on billionaires and a state-run health caresystem -- a huge chunk of the US economy. Both also dismiss the idea that their political purity is a vote killer.

Granted, what's considered "left" in the US is closer to center in the UK (where the state-run health care is generally beloved), but the two great Western democracies often rumble with similar trends. After all, the 2016 Brexit referendum to leave the EU foreshadowed Trump's own anti-establishment revolt in the same year. No one saw either coming.

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