ALEXANDRIA, Va.—Bad news for Hillary Clinton and Donald Trump: Undecided voters' disdain for both major-party presidential nominees seemingly knows no bounds. This helps to explain why the outcome of the presidential race remains up in the air. Undecided voters have trouble picturing either Democrat Clinton or Republican Trump as president, and are especially worried about each candidate's ability to serve as commander in chief.

All this was evident at a focus group of undecided voters in the key swing state of Virginia. Thirty of them gathered for a three-hour discussion conducted by Republican pollster Frank Luntz.

The commander in chief question may be the "make-or-break" issue of the campaign, Luntz said afterward in assessing the focus group, sponsored by AARP. Luntz said undecided voters tend to see the race as a matter of two bad options in Clinton vs. Trump. The pollster said the first general-election presidential debate on Sept. 26 could make all the difference.

"If the election is defined by whether you like or dislike Hillary Clinton, she loses," Luntz said. "If the election is defined by what you think of Donald Trump, he loses."

Luntz started the session Friday night by asking participants to describe Clinton and Trump in one word. The replies, spoken out loud by the participants one by one, were overwhelmingly negative. Clinton was described as untrustworthy, slimy, a liar, corrupt, crooked and willing to say or do anything to win the presidency. Trump was described as arrogant, unbalanced, crazy, phony, a bigot, a buffoon and garbage.

Twelve of the 30 said they would consider voting for Libertarian Party nominee Gary Johnson in the general election although their commitments to him seemed shaky.

The participants appeared to be relatively well-informed on issues. Given a long list of quotes or actions by Clinton and Trump, and asked what bothered them most about each item, most were very troubled by Clinton's saying she has never lied to the country, apparently because that statement itself was seen as a lie. The voters were also bothered by the fact that Clinton used a private email server when she was secretary of state, which suggested to participants that she was trying to hide something. Most were troubled by Trump's criticizing the Muslim parents of a U.S. soldier killed in Iraq, and for saying former prisoner of war John McCain, now a GOP senator from Arizona, was not a hero during the Vietnam War.

Most of the voters also disliked the attacks that Clinton and Trump are using against each other. The voters in the focus group said they wanted more specifics on how the candidates would solve problems such as bolstering Social Security and improving the tax system.