"We have a really important election tomorrow," Clinton said with a grin, speaking to a crowd in Allendale, Michigan.
She described the election as a choice "between strong and steady leadership or a loose cannon who could put everything at risk."
Clinton took a more serious tone as she relayed an anecdote about a former nuclear launch officer's response to Donald Trump's comments about using nuclear weapons.
"Imagine the responsibility," Clinton said, explaining the role that the officer had played. "A young air force officer in his twenties waiting to hear whether or not an order is given for him to launch nuclear weapons."
She described the process of ordering a nuclear strike.
"There is no appeal from a president's order to do that. The joint chiefs of our military forces can't say no, don't do it. There is no veto from Congress or anyone else," Clinton said. "The time between the order being given and the actual launch is four minutes."
She cited a letter written by ten former nuclear launch officers who said that Trump "should not have his finger on the button" and called the Republican nominee unfit to be commander-in-chief.
"The awesome responsibility that is housed in one person is something I want you to think about between now and the time you vote," Clinton said. "Because I will pledge to you that I will exercise the greatest care and responsibility in all of the powers invested in the office of the presidency."
She ended the rally with a call for unity.
"We need more of two things right now," Clinton said. "We need more love and kindness in America."
"We all have to start thinking about how we want to be treated, and what that means about how we treat others," she added, directing her closing argument to disaffected voters.
"Every one of us gets knocked down. The question, as my mother would say, is are you going to get back up?" Clinton said. "And for people in our country who feel like they've been knocked down and nobody cares, nobody's paying attention, here's what I want you to know. If you give me the honor of being your president, I'm going to do everything I can to get this country and everybody in it back up on our feet moving forward together."