Apparently, all it takes for Donald Trump to perform poorly in polls is the mere suggestion that an entire religion should be banned from the country he hopes to run.

A a Bloomberg Politics/Des Moines Register Iowa Poll released Saturday night shows that Sen. Ted Cruz is beating Trump by a total of 10 percent, seven weeks before the caucuses. From Bloomberg:

The firebrand junior senator from Texas is backed by 31 percent of those likely to attend the Republican caucuses that start the presidential nomination season on Feb. 1. Trump is a distant second at 21 percent, up slightly from 19 percent in October, but below his peak of 23 percent in August.

Among Iowa polls, Cruz’s 21-percentage-point spike since October is the largest surge over that past five presidential campaigns. Ben Carson, once thought to be a Trump challenger, fell by 15 percentage points, and is now trailing in third place.

Trump has already tweeted telling his followers “don’t trust the Des Moines Register poll” because it’s “biased toward Trump!” Yes, that’s probably it—the poll must be biased. It couldn’t be this, it just couldn’t be:

[Image via Getty]

Contact the author at melissa.cronin@gawker.com.