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Has Bernie Sanders finally made it? He is now officially part of Donald Trump’s stump speech. And not in a flattering way.

“How about this guy - this socialist Bernie sanders? This guys a total whack job,” Trump said at his morning rally in Norwalk, Iowa. He made a similar claim later in the day in Oklahoma.

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Trump’s focus on Sanders has intensified in recent weeks as Sanders' support has been increasing in polls, especially in early election states of Iowa and New Hampshire.

Trump held a rally in Sanders’ hometown of Burlington, Vermont the first week of January where Trump said, “At least Bernie is getting some action. He gets much smaller crowds than me, but at least Bernie gets some action right. Oh I would love to run against Bernie.”

Before that, Trump largely ignored Sanders in his campaign speeches, except to say that he made a major mistake by minimizing the controversy over Hillary Clinton’s email by saying at an early Democratic debate that no one cared about Clinton’s “damn emails.”

Now that Trump's attacks on Sanders have sharpened, it's a sign that Trump sees a potential threat to his electoral success.

Michael Briggs, a spokesman to Sanders, responded with this statement: "What's he talking about? Is health care whacko? Is he talking about making college affordable? Doing something about runaway prescription drug prices and helping seniors on Social Security? Is providing family leave for new parents something he regards as whacko? Maybe he's against raising the minimum wage or creating millions of good-paying jobs by rebuilding our crumbling roads and bridges. Is addressing the planetary crisis of global warming whacko? Oh yeah. I forgot. He thinks climate change is a hoax invented by the Chinese. C'mon."

Sanders said he is a threat to Trump, pointing to head-to-head polls.

“There was, I think it was a Wall Street Journal/NBC poll that came out yesterday or the day before. You know what it said? It said that Bernie Sanders defeated Donald Trump by 15 points, Hillary Clinton defeated him by 10 points,” Sanders told reporters when asked about Trump.