Transcript for VP Candidates Go on Attack in Debate Showdown
The vice presidential debate was supposed to be the civil, sober, and serious one. Waged between two traditional politicians who have been compared to sitcom dads. But Mike pence and Tim kaine spent 90 minutes talking over and past one another, most of it led by kaine, who once called himself boring but came into tonight's face-off clearly amped up. Did it work? Here's Abe bc's David Wright. Reporter: Tonight in Virginia, the JV debate. The two men battling it out to be a heartbeat away from the presidency each made their case. Six times tonight I have said to governor pence, I can't imagine how you can defend your running mate's position on one issue after the next. And in all six cases he's refused to defend -- Don't put words in my mouth. Reporter: Democrat Tim kaine fashioned himself the attack dog. The thought of Donald Trump as commander in chief scares us to death. Reporter: Forcing republican Mike pence to defend trump. I can't imagine how governor pence can defend the insult-driven, selfish, me-first style of Donald Trump. Senator, you and Hillary Clinton would know a lot about an insult-driven campaign. It really is remarkable. Reporter: Pence, poised and steady, deflected. Painting the democrats as mud slingers. The campaign of Hillary Clinton and Tim kaine has been an avalanche of insults -- You are a Donald Trump supremacist. Let me talk about this issue -- Senator, I think I'm still on my time. Isn't this a discussion? This is open discussion. Governor, you'll have an opportunity -- Let me finish my sentence. I appreciated the hired, fired then. You used that a whole lot. I think your running mate used a lot of dud lines. Reporter: Put on the spot over Donald Trump's taxes, specifically why hasn't he released his returns? And why did a leaked copy of his '95 return show that trump declared nearly a $1 billion loss, potentially reducing his tax liability to zero for 18 years? He went through a very difficult time, but he used the tax code just the way it's supposed to be used and he did it brilliantly. How do you know that? You haven't seen his tax return. He's created a business that's worth billions of dollars -- How do you know that? With regard to paying taxes this whole not paying taxes and people saying he didn't pay taxes for years, Donald Trump has created tens of thousands of jobs. Reporter: Kaine hit back. Donald Trump started this campaign in 2014. He said, if I run for president, I will absolutely release my taxes. And he will. He's broken his first promise. Second, he stood on -- He said he will. He stood on the stage last week, when Hillary said you haven't been paying taxes, he said, that makes me smart. So it's smart not to pay for our military, it's smart not to pay for veterans, it's smart not to pay for teachers, and I guess all of us who do pay for those things I guess were stupid. Reporter: As contentious as tonight's debate was in all honesty it can't compete with the clash at the top of the ticket. Ratings alone, Clinton versus trump round one, was the super bowl. The highest-rated debate in TV history. Tonight's contest, more like the world championship of darts. Entertaining enough. But bound to appeal to a much smaller audience. That said, consider this. Donald Trump, if elected, would be the oldest president ever. Hillary Clinton -- only a few years younger, and she's faced questions about her health. All the more reason to pay attention. Either one of these men could end up with the top job someday. Tonight, pence did his best to channel Ronald Reagan. There they go again. Reporter: Kaine tried to Ronald Reagan him right back. Ronald Reagan said something interesting about nuclear proliferation in the 1980s. He said, the problem with nuclear proliferation is that some fool or maniac could trigger a catastrophic event. And I think that's who governor pence's running mate is. Oh, come on. Exactly who president Reagan warned us about. Senator, that even beneath you and Hillary Clinton. That's pretty low. Is everybody ready to win big tomorrow? Reporter: Kaine came into this debate with a reputation of Mr. Nice guy. I want to make it very clear he's trying to fuzz up what Donald Trump has said. Reporter: Tonight he did his level best to throw sharp elbows. He's got kind of a personal Mt. Rushmore. Vladimir Putin, Kim jong-un. Please. Moammar Gadhafi, saddam hussein. Oh, come on. The game plan was to be aggressive and he definitely was too aggressive. Especially in comparison to pence. Who was trying to come across as a very calm, cool, collected candidate. Reporter: In one exchange accusing trump of being the political equivalent of a super villain. Donald Trump believes that the world will be safer if more nations have nuclear weapons. I'd love to hear governor pence tell me what's so enjoyable or comical about nuclear war. Governor pence? Did you work on that one a long time? That had a lot of creative lines in it. I'm going to see if you can defend any of it. I can defend -- Reporter: In the middle of the defend, Donald Trump retweeted that kaine looked like an evil crook out of the Batman movies. That is absolutely false and you know it. Absolutely truth. Reporter: For both men this was a coming-out party, the first time they'd been tested on a national stage. Although their bosses bickered plenty last week. For 30 years you've been doing it. And now you're just starting to think of solutions. Actually -- Excuse me. I will bring back jobs. You can't bring back jobs. Well, actually, I have thought about this quite a bit. Richard Nixon -- Reporter: The understudies were arguably even worse. Gentlemen, the people at home cannot understand either weave you when you speak over each other. These guys, and Donald Trump has said it, deportation force. They want to go house to house, school to school, business to business, and kick out 16 million people. And I cannot -- That's nonsense. I cannot believe -- Reporter: Pence pushed back. We have a deportation force called immigrations and customs enforcement. And the union for immigrations and customs enforcement for the first time in their history endorsed Donald Trump to be the next president. Reporter: Pence was scrupulously polite. Ever the grownup. Mr. Trump has said -- A nation without borders is not a nation. Donald Trump has committed to restoring the borders of this nation. Reporter: Unlike his boss, pref preternaturally calm, refusing to take the bait. Trying to keep up with the insult-driven campaign -- I'm saying facts about your running mate. Senator, please -- Don't put words in my mouth, and I'm not defending him. You're not. Most of what you've said is completely false and the American people know that. I'll run through the list of thing hts. Senator, please -- One canned date blatantly not telling the truth in a lot of situations, that will be Mr. Pence. And then the other candidate, kaine, who didn't come across likeable because he kept interrupting, he kept appearing to be rude. Reporter: Being a vice presidential candidate may be a thankless job. But for both men the outcome of this debate has huge implications. The one whose boss loses will likely be waiting in the wings to run for the top job four years from now. The other will be waiting in the wings much, much closer. I'm David Wright for "Nightline" in New York. Thanks to David Wright. Sunday night the second presidential debate, just five days away. And it will be co-moderated by our own Martha Raddatz. Full team coverage here on ABC on Sunday night.
This transcript has been automatically generated and may not be 100% accurate.