Donald Trump continued railing against what he says is voter fraud Monday night, this time claiming that “illegal immigrants are voting all over the country.”

“There is tremendous voter fraud. And how Republican leadership doesn’t see that is beyond me,” Trump told Fox News before a Green Bay, Wisconsin, rally.

“So many cities are corrupt and voter fraud is all too common,” Trump said a short time later from the stage.

He went on at length, citing a Washington Post blog post by two political scientists who estimated that there were enough non-citizens (but not unnecessarily undocumented immigrants) who voted in 2008 to have affected the outcome of the Senate race in Minnesota, won by Democrat Al Franken, and the presidential race in North Carolina, won by President Barack Obama.

But that post, based on a longer article in the journal Electoral Studies, was quickly and roundly criticized for relying on data from an online survey in which respondents chose to participate, rather than a random sampling typical of scientific polls.

Trump has for weeks been claiming ― without evidence ― that the November election will be stolen from him through improper voting “in certain areas,” referring, he acknowledged, to large cities like Philadelphia.

Trump’s assertions have drawn rebukes from even Republican elections officials, and have caused some of his allies to try to restate his allegations as more general warnings of something that might happen or, in the case of his running mate Mike Pence, as a criticism of the news media for favoring Democratic nominee Hillary Clinton.

But Trump continues to insist that significant voter fraud is occurring today. In a tweet Sunday afternoon, Trump wrote: “The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary ― but also at many polling places – SAD.”

He followed it up Monday morning with this: “Of course there is large scale voter fraud happening on and before election day. Why do Republican leaders deny what is going on? So naive!”

Trump has long blamed undocumented immigrants for many of the country’s woes, from taking jobs away from American citizens to committing a disproportionate number of violent crimes. He opened his campaign in June 2015 by claiming that Mexicans coming across the border illegally were rapists and criminals and has promised to deport the 11 million undocumented immigrants in the country.

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.