CHICAGO — Democratic presidential nominee Hillary Clinton avoided a direct answer Thursday on whether libertarian Gary Johnson is qualified to be president, but she had a subtle warning for Democrats flirting with voting for the third-party candidate.

"Either Donald Trump or I will be the president of the United States," she told reporters traveling with her. "So people have to look carefully in making their decision about who to vote for, because it will be either him or me. And I am going to do everything I can to make sure it’s me."

That was an indirect way of saying what other Democrats are saying in more blunt terms: that a vote for Johnson, whether in support of his ideas or as a protest against the unpopular Clinton, could make it easier for Trump to win.

Johnson is polling in the low single digits nationally but could be a spoiler in a few states, including New Hampshire, a swing state Clinton visited Wednesday.

Clinton ignored a question about whether Johnson's inability to name a foreign leader he admired should disqualify him from contention. But the former secretary of state did have a ready answer, and a hearty laugh, when asked for her own favorite foreign leader.

"Oh, let me think," Clinton joked, theatrically. "No, look, I like a lot of the world leaders. One of my favorites is Angela Merkel, because I think she’s been an extraordinarily strong leader during difficult times in Europe which has obvious implications for the rest of the world, most particularly our country," Clinton said.

"Her leadership and steadiness on the euro crisis and her bravery in the face of the refugee crisis is something that I am impressed by."