WASHINGTON (AP) — Law enforcement officials are bracing for the possibility of massive unrest at the polls on Election Day, Nov. 3.

They're conducting drills, setting up command centers and warning the public.

It comes in the wake of claims by President Donald Trump and his allies that the vote will be rigged and his call to supporters to “go into the polls and watch very carefully.”

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Tensions across America are high following increasing political polarization and months of mass demonstrations against racial injustice that have seen violence by the left and right. Gun sales are way up.

And extremist groups are emboldened after Trump told one group to “stand back and stand by."