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First of all, let me go on record as saying I've never thought Joe Biden would win the Democratic presidential nomination. Biden is this election's Rudy Giuliani. Rudy was the big name in the 2008 GOP primary. Everyone thought he was unbeatable. He never won a single state and quickly dropped out of the race.

I've argued for many months that Biden will go nowhere in this Democratic primary. First and foremost, Democrats don't want a straight old white male.

Then there's Biden's mind. It's clearly not functioning at top speed anymore. Biden is not just old but slow and foggy. He could never be the president. Time has passed him by.

And then there's Ukraine. Forget President Donald Trump. It's Biden's political career that was destroyed by this Ukraine story. Americans know something smells rotten about the Bidens in Ukraine. Even if it's not criminal, it's certainly dirty. That disqualifies Biden.

The problem is Democrats have no other candidate. So Biden, for better or for worse, remains the front-runner for the Democratic presidential nomination.

But in Thursday's debate, he committed a major sin. He alienated his base -- the only group in the party that still backs him. In speaking of economic growth, the moderator asked, "As president, would you be willing to sacrifice some of that growth, even knowing potentially that it could displace thousands, maybe hundreds of thousands, of blue-collar workers, in the interest of transitioning to that greener economy?'"

Biden answered quickly and boldly: "The answer is yes."

End of story. There's your Trump TV advertisement. Even if Biden somehow still wins the nomination, Trump will destroy him with working-class and middle-class voters.

The follow-up in a debate between Trump and Biden would be equally powerful. Biden would claim that those workers would all find new jobs in the "green economy."

Trump would answer: "Really? Like Solyndra? Like many green companies that received billions of taxpayer dollars under Obama-Biden? They're out of business. Billions lost forever on a pipe dream. A liberal fantasy. Good luck. I'll stick with oil and gas jobs. The average one pays $150,000 a year. Anyone want to give up your job for Joe's nonexistent green jobs? You want to take that chance, vote for Joe. I dare you."

The only hope Biden had was to gain the support of white working- and middle-class voters in places such as Pennsylvania, Ohio, West Virginia, Michigan and Wisconsin. Now they're gone -- forever. Middle-class workers will never gamble their jobs on Biden's green jobs -- not unless they also like cold toilet seats, warm beer and broccoli as the main course for dinner.

Trust me, the Democratic Party's presidential candidates -- even supposedly moderate Joe Biden -- are now officially poison to working- and middle-class America. It's not even close. It's Trump by a mile.

By the way, here's a quick snapshot of the electorate before Biden's deadly words. One of my friends runs a Las Vegas construction company. He loves Trump. His annual revenues are up from $17 million to $65 million under Trump. He says every single construction worker he meets -- steelworkers, plumbers, electricians, machinists -- all support Trump. These are union guys. That was before Biden's words on Thursday.

My advice to Democrats: Order your depression pills. Get your minds prepared for five more years of Trump. The deal is done.

Wayne Allyn Root is a CEO, entrepreneur, best-selling author, nationally syndicated talk show host on USA Radio Network and the host of "The Wayne Allyn Root Show" on Newsmax TV nightly at 8 p.m. ET.