Maureen Groppe

USA TODAY

WASHINGTON — Tim Kaine describes himself as "boring." Mike Pence calls himself a “B-list Republican celebrity.”

No one expects Tuesday's debate between the two vice presidential nominees — Kaine, a Democratic senator from Virginia, and Pence, the Republican governor of Indiana — to draw the record-breaking 84 million people who watched the first faceoff between presidential candidates Hillary Clinton and Donald Trump.

But viewers who do tune in could be rewarded with a clearer sense of the differences between the two parties than could be gleaned from the Clinton-Trump debate.

Clinton-Trump debate sets ratings record

“The vice presidential debate will be two competent politicians discussing issues,” said Elaine Kamarck, an expert at the Brookings Institution. “There won’t be the distraction that Trump, especially, brought to the presidential debate.”

Voters may have another reason to watch: to learn something about the men vying to become second in line to the presidency, each of whom remains unknown to many Americans.

Neither Kaine, 58, nor Pence, 57, had large national profiles when they were selected as vice presidential candidates. And both have been overshadowed by their well-known — and polarizing — running mates.

As a result, polls show more than one-third of voters don’t know enough about either to form an opinion.

“To some extent, this is still their introduction to a big part of the public,” Joel Goldstein, a vice presidential expert at the Saint Louis University School of Law, said of Tuesday's debate. “Clinton and Trump have clearly been the focus, and Kaine and Pence are less-captivating, (less-)exciting figures.”

Both running mates have long records in government and extensive public speaking experience, although this will be their first nationally televised debate.

“We’ve got a sitting United States senator versus a former House member who spent years as a radio talk-show host,” said Jim Manley, a Democratic strategist and former aide to Senate Minority Leader Harry Reid, D-Nev. “As far as I’m concerned, they’re coming into the debate pretty even. Both are articulate and think well on their feet.”

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Both are also well-matched in temperament. Kaine and Pence are affable with low-key, sunny demeanors. They’re known as nice guys, even by those on the other side of the aisle.

But despite the value they place on civility, they’re not pushovers.

“He’s a consummate gentleman, but that doesn’t mean he isn’t tough,” Wayne Turnage, who served as Kaine’s gubernatorial chief of staff, said of his former boss.

Tom Rose, a close friend and adviser to Pence, called Indiana’s governor a gracious man who will be very respectful.

“But he can throw an uppercut, too,” Rose said.

At the debate, Pence likely will be more focused than Trump was in attacking Clinton’s vulnerabilities, including her use of a private email server while secretary of State, her comment that half of Trump’s supporters were a “basket of deplorables,” and allegations that the Clinton Foundation was part of a pay-to-play scheme. Throughout the campaign, Pence has been the more disciplined messenger — as well as a "clarifier in chief" — for some of Trump's controversial remarks.

“Pence is much more of a normal politician than Trump is,” Kamarck said. “I think Pence will be sort of steady and try to calm people’s worries.”

Kaine likely will challenge Pence on Trump’s comments about women, his business practices and his refusal to release his tax returns.

“I’m looking for Sen. Kaine to find new and creative ways to try and make Pence defend all sorts of Trump’s controversial comments,” Manley said.

Pence undoubtedly will be asked about Trump's recent criticisms of former Miss Universe Alicia Machado's weight gain and his tweet that people should check out a sex tape of her. (There's no evidence such a tape exists.)

Asked how Pence will address the issue, spokesman Marc Lotter said the Indiana governor is focused on the clear choice the election offers between Trump's and Clinton's visions for the future.

Kaine could repeat criticisms he’s made on the stump about the controversial “religious freedom” law Pence signed as governor. Kaine, who focused on civil rights cases while a lawyer in private practice, has called Pence’s record on LGBT issues “anti-civil rights.”

Pence told conservative radio talk-show host Hugh Hewitt he’s ready to respond.

“I don’t believe in discrimination against anyone because of who they are or who they love, and anyone who knows me knows that to be the case,” Pence said Monday.

Pence, though, could have trouble pivoting to a general election audience when one of the assets he brought to the ticket was a record that appeals to social conservatives. In recent weeks, Pence has made several appearances before social conservative groups, touting his opposition to abortion and his long-standing fight against Planned Parenthood.

Trump didn’t do much in his debate against Clinton to appeal to independents, particularly women, and Pence might not be able to help, said Mitchell McKinney, who teaches political communication at the University of Missouri.

“I don’t see that Pence is able to make appeals to that segment of the slice of the electorate that maybe Trump really needs to work on,” McKinney said. “He’s not the messenger to do that.”

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Kaine, who personally opposes abortion but has said it’s a moral decision for people to make for themselves, has gotten mixed reviews from reproductive rights groups over the years.

Pence has gotten debate advice from House Speaker Paul Ryan, R-Wis., who faced off against Joe Biden in a vice presidential debate four years ago. And he’s been running through practice debates, with Wisconsin Gov. Scott Walker playing the role of Kaine.

Walker playing Kaine in mock debate

Rose said Pence has focused on mastering the policy positions of both campaigns in order to present a clear contrast.

“The challenge at that level for any candidate, not just Gov. Pence, is more comfort and poise and delivery and presentation than it is canned policy answers,” Rose said. “He’s very comfortable conveying his philosophy.”

The Clinton campaign did not respond to requests for comment about Kaine’s debate preparation. Robert Barnett, a prominent Washington lawyer who played the role of Vermont Sen. Bernie Sanders in Clinton’s primary debate prep, has portrayed Pence during Kaine’s debate practice.

While Kaine has a lot of debate experience, he told CBS it's new for him to take the stage to promote and defend someone else's record.

"This is a different one because it`s not really Pence v. Kaine," he said.

Turnage said Kaine is a policy wonk, but his years as a litigator also honed his skills for explaining things to the average person.

“You will see his sincerity. You will see his intellect. And you will see his depth of knowledge on public policy on full display,” Turnage said.

TV viewership for vice presidential debates, which began in 1976, is typically at least 20% smaller than for presidential debates. But vice presidential debates have produced memorable moments. There’s Lloyd Bentsen’s “You’re no Jack Kennedy” putdown of Dan Quayle, Bob Dole’s 1976 comment that all the wars in the past century were “Democrat wars,” and Ross Perot running mate James Stockdale’s rhetorical "Who am I? Why am I here?" comment.

But it's rare that a vice presidential debate, or the running mates themselves, affect the outcome of a presidential election.

“It’s not going to be a Sarah Palin year,” McKinney said, referring to the 2008 vice presidential debate that was unique for drawing more viewers than that year’s presidential debates. “There’s the personality of these candidates — from vanilla to milquetoast.”

That doesn’t mean Kaine and Pence won’t feel the pressure.

A Palin aide suggested she try to calm herself before the 2008 debate by imagining hair plugs on Biden. Biden, meanwhile, got loose before walking on stage by stretching his quads and rolling his neck.

Before Pence's big speeches or rallies, he usually gets a squeeze of the hand and a kiss on the cheek from his wife, Karen, and they share a moment of reflection and prayer, according to Lotter. Pence’s trademark unflappability comes from being deeply religious and his belief “in an ultimate purpose and destiny for all of us,” Rose said.

Plus, Rose added, Pence jokes that as he's gotten older “he’s discovered the shortest distance between two points is a nap.”

Vice presidential debate

When: 9-10:30 p.m. EDT, Oct. 4

Where: Longwood University, Farmville, Va.

Who: Democratic Sen. Tim Kaine and Republican Gov. Mike Pence

Format: The debate will be divided into nine time segments of approximately 10 minutes each.

Moderator: Elaine Quijano, CBS News correspondent and anchor for CBSN, CBS’s digital streaming network.

Viewership: With the exception of the 2008 debate between Joe Biden and Sarah Palin, the television audience for vice presidential debates is less than for the presidential debates. In 2012, 51.4 million people watched Biden debate GOP Rep. Paul Ryan, compared with the 67.2 million viewers for that year’s first presidential debate. This election’s first faceoff between Republican Donald Trump and Democrat Hillary Clinton drew an estimated 84 million viewers, a presidential debate record.