Sen. Barack Obama (D-Ill.) had harsh words on Monday for Bill Clinton, saying that the former president’s campaigning on behalf of his wife, Sen. Hillary Rodham Clinton (D-N.Y.), has risen to a “pretty troubling” level.

“I completely understand him wanting to promote his wife’s candidacy,” Obama said. But he added that there “should be some standards of honesty in any political discourse.”

“If you have something that just directly contradicts the facts and it’s coming from a former president, I think that’s a problem, because people presume that a former president is going to have more credibility,” the Illinois senator said in an interview with ABC’s “Good Morning America.” “And I think there are certain responsibilities that are carried with that.”

Obama called the Clintons “two formidable opponents” and accused the former president of “spending most of his time attacking me.”

Meantime, the former president said in an interview with NBC that Dr. Martin Luther King Jr. would have been excited about Obama’s campaign, and he praised his wife’s opponent as “a great speaker, a smart man, someone who loves our country.”

Bill Clinton added that he believes King “would get a kick out of the fact that it appears the nominee of the Democratic Party would either be an African American senator who’s profoundly eloquent, or a woman senator who got her Methodist youth minister to take her to see Dr. King when she was a young high school student, who shared his lifelong commitment and who idolized him.”

The former president also said he was pleased to see that neither of the candidates appeared to be losing votes because of their race or gender.