Analysis by Chris Cillizza, CNN Editor-at-large

(CNN) -- Over the weekend at a campaign rally for Sen. Dean Heller (R) in Nevada, President Donald Trump said this:

"I don't think we like sanctuary cities up here.

"By the way, a lot of people in California don't want them, either. They're rioting now. They want to get out of their sanctuary cities. You know, there's a big turn being made, folks. A lot of these sanctuary cities you've been hearing about in California and other places, but California, they want to get out, they're demanding they be released from sanctuary cities."

While Trump's language makes it somewhat unclear what exactly he means, he is suggesting that Californians are up in arms -- to the point of rioting -- about sanctuary cities (places where undocumented workers are not turned over for deportation) in their state.

The problem with Trump's claim is that there is no actual evidence of riots in California over sanctuary cities. As the San Francisco Chronicle's Annie Vainschtein noted on Sunday:

"It's true that sanctuary cities have been a reliable topic of conversation and, particularly in the context of high-profile crimes such as the murders of Kate Steinle and Mollie Tibbets -- homicide cases involving undocumented immigrants that received national attention -- a source of contention. But there has yet to be any evidence of rioting, especially in California."

The undocumented immigrant accused of killing Steinle was acquitted in December 2017.

When I asked for examples of what Trump could be talking about on Monday, one reader pointed me to a story headlined: "Violent Protest Erupts In Berkeley, At Least 20 Arrested." I read the piece. There are two obvious problems with using it as evidence that makes Trump's claim true:

1) It's from August. It's October now and Trump was speaking in the present tense when he said "they're rioting now."

2) The violence the story reports on had nothing to do with sanctuary cities. Here's the first paragraph of the piece: "At least 20 people were arrested, many armed with a variety of weapons, after a rally turned into a violent clash between anti-fascist and anti-Marxist protesters near a Berkeley park Sunday afternoon." Violent clashes are never good. But, to say this has anything to do with sanctuary cities -- the word "sanctuary" is never mentioned in the story -- is a total and complete swing and a miss.

Trump himself was asked by NBC's Geoff Bennett for proof of his riot claims as he left the White House Monday to headline a rally for Sen. Ted Cruz (R) in Texas. Here's their exchange:

BENNETT: Hey, Mr. President, you said Californians were rioting over the sanctuary cities. Where?

TRUMP: You shouldn't have -- take a look. They want to get out of sanctuary cities. Many places in California want to get out of sanctuary cities.

BENNETT: But that's not rioting, sir, right?

TRUMP: Yeah, it is rioting in some cases.

BENNETT: Where are the riots, sir?

Trump moves on to the next question, never answering Bennett. The reason, of course, is because there is no answer. Or proof. Or even a speck of evidence.

What's remarkable is not that Trump said something that is demonstrably false. According to a count maintained by The Washington Post's Fact Checker blog, Trump made more than 5,000 false or misleading claims in his first 601 days in office.

What's remarkable is that no one -- or very few people -- within Trump's base will bat an eye at the fact that his California riots claim is entirely, well, fact-free. They believe him, whether or not the facts bear out that belief.

Here's the thing: Facts -- no matter what Trump says -- are not a partisan position. There aren't two sets of facts based on whether you are a Democrat or a Republican. There are just facts. Some claims are based on established facts. Others are not. Trump's claims about riots on sanctuary cities in California are simply not backed up by facts.