Swing-state GOP senator calls on Trump to apologize to the Khans

Sen. Ron JohnsonRonald (Ron) Harold JohnsonOvernight Health Care: House passes .3T omnibus | Bill boosts funds for NIH, opioid treatment | Senators spar over ObamaCare fix | 'Right to Try' bill heads to the Senate GOP pushes to change Senate rules for Trump House passes 'right to try' drug bill MORE (Wis.), who faces a tough reelection race in November, on Wednesday joined the Republicans calling on Donald TrumpDonald John TrumpScarborough mocks 'Deflection Don' over transgender troop ban Pelosi condemns Trump's 'cowardly, disgusting' ban on transgender troops Trump moves to ban most transgender people from serving in military MORE to apologize for his comments to the parents of Army Capt. Humayun Khan, a Muslim soldier who was killed in Iraq in 2004.

Johnson, considered among the most endangered incumbents as he faces former Sen. Russ Feingold (D-Wis.), had previously praised the Khans, who spoke at the Democratic National Convention last week, in a statement that made no mention of Trump.

But on Wednesday he went further in an interview with WTMJ radio, as first reported by The Associated Press, calling on the GOP presidential nominee to say he's sorry for attacking Khans.

"I’ve spoken to a number of Gold Star moms and dads, and they just deserve our utmost respect. What else can you say? I can't put myself in their position — I can't imagine losing a child. I can’t imagine that sacrifice. So all you can do is respect it and honor it and that’s all that you should do," Johnson said.

"He should apologize," he added.

Trump had slammed Khizr Khan, saying he had no right to question his views on the Constitution. He also suggested Khan's wife was not allowed to speak at the convention because of her religion.

On Tuesday, New Jersey Gov. Chris Christie, the first of the 2016 White House hopefuls to endorse Trump, said his response was "inappropriate."

And a spokeswoman for House Speaker Paul RyanPaul Davis RyanYou just can't keep good health policy down Trump blasts Congress for sending him omnibus bill that 'nobody read' Students bash Congress for inaction on gun control MORE (R-Wis.), AshLee Strong, said that the Speaker "rejects" Trumps criticism.

"The Speaker has made clear many times that he rejects this idea, and himself has talked about how Muslim Americans have made the ultimate sacrifice for this country," she said.

Trump on Tuesday said that he did not regret his statements, including responding to Khan's questions about his sacrifices by discussing his successful business career.

"I don’t regret anything," Trump said.

"I said nice things about the son, and I feel that very strongly. But, of course, I was hit very hard from the stage, and you know it’s just one of those things — but, no, I don’t regret anything."