“The reason Republicans lost can be summed up in two words: ‘47 percent,’ ” Mr. Cruz said.

The comments came during a forum in California moderated by ABC’s Jonathan Karl with Mr. Cruz, Sen. Rand Paul of Kentucky and Sen. Marco Rubio of Florida in one of the first debate-style settings of the 2016 presidential cycle.

Mr. Romney, in secretly videotaped remarks during the 2012 campaign, appeared to write off nearly half the country as largely entitlement-dependent who would vote for President Obama no matter what — comments that dogged him for the rest of the campaign and which Democrats have continued to try to hold up as the general thinking of the Republican party.

Mr. Rubio said Mr. Romney “ran the best race he possible could” and that he didn’t want to second-guess the campaign.

Mr. Paul invoked past words from Mr. Romney’s wife on another possible run by Mr. Romney in 2016: “I’m kind of with Ann Romney on this one — no, no, no, no, no.”