When Donald Trump heads to Chicago next week, he might want to steer clear of Wrigley Field. In an interview with the Chicago Sun-Times' Michael Sneed, the Republican front-runner continued his feud with the Ricketts family, who own the MLB's Chicago Cubs, and are also funding a group attacking him.  

Trump said he was scheduled to deliver a speech in Chicago next Friday. Now a new group funded by Marlene Ricketts, the matriarch of the family that owns the Cubs, is attacking Trump, questioning his conservative bona fides and condemning him for using undocumented foreign workers in construction projects. The group now reportedly plans to run attack ads in a bid to stop Trump's march to the nomination. When asked about the feud with the Cubs owners, Trump told the Sun-Times the Ricketts family should perhaps focus on sports and leave the presidential race alone. 

"I think the Ricketts family should be spending their time trying to develop a championship team and less time trying to demean Donald Trump," he said. "They should spend less time worrying about me. They don’t know me."

Marlene Ricketts put $3 million toward Our Principles PAC, which is set to run an ad in Illinois, Florida and Michigan — states that vote soon — that calls into question the defunct so-called Trump University, which is accused of fraud, according to the Chicago Tribune. A narrator in the ad says, "Donald Trump belongs in 3 a.m. infomercials," and not the White House. 

Trump had previously tweeted, "I hear the Ricketts family, who own the Chicago Cubs, are secretly spending $'s against me. They better be careful, they have a lot to hide!" That prompted Tom Ricketts, the Cubs chairman and son of Marlene, to tell reporters at spring training in Arizona, "It's a little surreal when Donald Trump threatens your mom."

Nebraska Gov. Pete Ricketts, a Republican who is the brother of Tom and son of Marlene, has not yet endorsed a presidential candidate, although as the Lincoln Journal-Star reports, it's safe to assume it won't be Trump. "Certainly I've got a very politically active family who care very much about this country," Ricketts told the Nebraska capital's newspaper after being questioned about his family's Trump feud. "So my family does get involved in the different aspects of our public policy debate, and of course we want to make sure that we have the best nominee here on both sides of the aisle."

Another Nebraska Republican, U.S. Sen. Ben Sasse, is an outspoken foe of Trump and vows to support a third-party option if he is nominated.   

trump chicago Demonstrators hold up a piñata of Donald Trump during a protest outside Chicago's Trump Tower on Oct. 12, 2015. Photo: Getty Images/Scott Olson

The interview with the Sun-Times revealed the GOP candidate's plans for a March 11 speech in Chicago in a boasting, meandering fashion typical of Trump.

"I’m planning to give a speech and stay at my world famous hotel, the Trump Tower," he said. "I love Chicago. I love Mike Ditka . I love my hotel ... the Trump Tower, which is No 1. We are No 1. No. 1. And how about my polls. Amazing, huh?"

Trump, and the local Trump Tower specifically, previously stirred up controversy in the Windy City when the mogul in 2014 stuck 20-foot letters spelling out his name on the side of the skyscraper, distressing some Chicagoans (including the mayor) protective of the city's much-loved skyline.

"It burns, it offends that this swollen outsider has in effect lifted his leg to mark his territory on our skyline in such a prominent way," wrote Chicago Tribune columnist Eric Zorn.