Mitt Romney's inexplicable compulsion to fudge facts continued in Thursday's debate, threatening to undermine his credibility over the long term. Romney's blurring came, as in previous debates, when he was challenged on his past.

On Thursday, his two most noticeable fibs involved whether he'd seen an ad -- a reprise of an earlier debate dodge -- and the nature of one of his investments.

The ad in question attacked Newt Gingrich for saying that Spanish is "the language of the ghetto." Romney, however, turned to Gingrich and said he didn't know whether the ad was true or not and wanted Gingrich to clarify.

"Let me ask the speaker a question. Did you say what the ad says or not? I don't know," Romney said.

CNN staff dug up the ad and Blitzer read the script to the candidates. Blitzer noted that Romney finished the ad by saying he approved the message.

At an earlier debate, Romney had deflected responsibility for super PAC attack ads, saying, "And with regards to their ads, I haven't seen them." Seconds later, he spoke as if he'd seen the ad. "The ad I saw said you were forced out of the speakership," Romney said.

The second truth question involved Romney's investment in Fannie Mae and Freddie Mac, which Romney said was in a "blind trust" managed without his knowledge by a trustee.

"What my trustee did is he loaned money to Fannie Mae and Freddie Mac. And they got paid interest," Romney said. "But what the speaker did was get paid to promote Fannie Mae and Freddie Mac."

But, as the Boston Globe reported, the Fannie and Freddie investments were not in the blind trust: "Unlike most of Romney’s financial holdings, which are held in a blind trust that is overseen by a trustee and not known to Romney, this particular investment was among those that would have been known to Romney."

Romney adviser Eric Fehrnstrom acknowledged that not all of the Fannie and Freddie investments were managed by a blind trustee. "But," he wrote in an email, "in both cases the investments are not selected by Gov. Romney and he has no control over them."

Fehrnstrom added: "The campaign has produced 85 videos, TV ads and radio spots." Romney "doesn't recall every one."