Collins, who has been critical of the tone of Trump's presidential campaign, says Trump's pick for vice president will offer a clue as to whether he is prepared to moderate his hard-edged campaign.
"This evolves daily. There are surprises daily. And I'm going to see what happens at the convention," Collins told David Axelrod on "The Axe Files" podcast, produced by CNN and the University of Chicago Institute of Politics. "It's going to be very important to me whom Donald Trump chooses as his running mate. That is arguably the most important decision that a candidate can make."
Specifically, Collins said she wants to see if Trump will pick a running mate who can "balance out some areas in foreign policy where he does not have experience."
In the Senate, Collins has worked with Trump's presumptive opponent in this fall's election, Hillary Clinton, and she described to Axelrod her frustration with some of Trump's attacks on the former New York senator.
"I don't like that Donald Trump calls anyone names," she said. "I think that is un-presidential and not worthy of the kind of public discourse that we should have. And I have been critical of him for criticizing Hillary Clinton for 'playing the woman's card.' I think that demeans her accomplishments and, as a woman, I'm particularly concerned when someone demeans the accomplishments of someone who has done a lot in her life, even if I don't agree with that person."
"And I should make clear," she added, "that Hillary and I have very different philosophies when it comes to the role of government and we disagree on some major issues, but that doesn't mean that I didn't work well with her when she was in the Senate. I did."
To hear the whole conversation with Collins, which also touched on her nearly 20-year career on Capitol Hill, whether she might run for governor of Maine and more, click on http://podcast.cnn.com
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