Transcript for 'You have to look at who is going to win' over Trump, Dr. Jill Biden says
Joe Biden's wife, Dr. Jill Biden, and what she said about her husband, even if he's not your favorite candidate. That that should not be the deciding factor, according to here's Mary Bruce. Reporter: Jill Biden with a blunt appeal to voters. You may like another candidate better, but you have to look at who is going to win. Reporter: Her pitch, even if you're not with Joe Biden on every issue, you should support him anyway if you want to beat trump. You know, your candidate might be better on, I don't know, health care than Joe is, but you've got to look at who is going to win this election. And maybe you have to swallow a little bit and say, okay, I personally like so and so better, but your bottom line has to be that we have to beat trump. Reporter: In Iowa today, the former vice president asked about his wife's comments. She was making the case, you should pick the person you think could win, because none of our issues will matter if Donald Trump wins. That was the point she was making. Reporter: It's also the point he's making in his first campaign ad. We have to beat Donald Trump and all the polls agree Joe Biden is the strongest Democrat to do the job. Mary, any reaction tonight from the other democratic candidates? Reporter: Well, David, no response directly to Jill Biden's come pents, but Biden's opponents say they can beat trump, too. They argue that voters don't have to make this choice, that they can follow their principles and still defeat the president. David? Mary Bruce live in Washington. Thank you, Mary.
This transcript has been automatically generated and may not be 100% accurate.