CHICAGO (CBS) -- He once called President Barack Obama the "Drug Dealer in Chief."

Now U.S. Sen. Mark Kirk (R-IL) is catching flak.

His Democratic opponent and her African-American allies are demanding an apology.

But CBS 2 Political Reporter Derrick Blakley reports Kirk isn't backing down.

U.S. Rep. Tammy Duckworth (D-IL), Kirk's opponent, said his comments about the president were beyond pale.

"Kirk has just joined the rogue's gallery of the president's fiercest and most unhinged critics and for that he should be ashamed….Sen. Kirk should apologize immediately," said Duckworth, who is running against Kirk in the November election.

Last week, Kirk called the $400 million cash payment to Iran, ransom for the release of U.S. hostages, saying "We can't have the president of the United States acting like the drug dealer in chief."

"If you look at all of the things he said, he lacks the ability to control what he's saying and you can look at the numerous gaffes that he's had over the years," Duckworth said.

In April, Kirk said he supported black businesses so the black community "is not the one we drive faster through."

And in May, again on the Iran deal, Kirk said, "President Obama just wants to get nukes to Iran." He later apologized.

"This is the same man who called one of his colleagues a 'bro with no ho.' It's not befitting of a United States senator," Duckworth said.

But in a statement Tuesday, Kirk didn't back down, saying the shadowy details of the Iran payment "seems more representative of nefarious deals than the conduct of the world's greatest democracy."

Kirk charged the president's actions were reckless, but Duckworth's allies say the same about Kirk's language.

"With him, it's a pattern of irresponsible, offensive rhetoric as well as personal insults directed at this president," State Rep. Christian Mitchell (D-26th) said.

Kirk insists the Iran deal will endanger more Americans abroad, while that American cash will be used to fund terrorism. But he may give more reaction once he faces reporters downstate in Quincy, Ill. Wednesday.