"All of these people are going to be in in Washington in a way that they haven't been there before, because they feel, and I think it's true, that the political winds are changing. That even within the Republican Party, there is a demand for some kind of reaction. And it can't be anemic," she told Powerhouse Politics podcast hosts Jon Karl and Rick Klein.
She points her finger at former colleague and Senate Majority Leader Mitch McConnell.
"I think the debate is going to be very wide-ranging, and I think it is pathetic that Mitch McConnell has said, 'I'm waiting for the president,'" she said. "He is a political leader who could care less about the Senate doing its job."
It was 2013 when Heitkamp, a freshman senator, joined with three other Democrats and most Republicans to oppose expanding background checks during commercial gun sales. At the time, she defended her controversial vote, saying she was listening to her constituents. But she senses a big change now, and is focused on leaders like Republican Senator Susan Collins from Maine, who could play more of a leadership role on gun reform.
Heitkamp said she believes McConnell is worried that the president will once again burn him.
"The president's been pulling the rug out from underneath McConnell," Heitkamp continued, "and McConnell says, 'Look, we've got vulnerability in my caucus. I'm not going to make those folks walk the plank unless they have the protection of the president.
She also warned that lawmakers have to be careful about linking mental health issues with gun ownership because people might become more hesitant about addressing conditions like depression.
"If you are prone to depression, if you have a mental health challenge, and you know going in and getting a prescription, going in and getting treatment, will eliminate your gun rights, I will tell you people won't seek treatment for their mental health challenges," she said, stressing that red flag laws are not anti-mental health. "What they are is helping families who say, 'Oh my goodness, my kid could do this or my neighbor could this.'"
Trump focused on mental health when he took reporters' questions at a White House event on Wednesday. Trump continued to be vague on specifics about gun reforms, but he did not mince words when it came to mental challenges: "I support keeping guns out of the hands of sick people, mentally ill people." He added: "We're going to be looking at a lot of things and hopefully coming up with something that's bipartisan -- has to be bipartisan."
Heitkamp said she's looking forward to the Democratic debate in Houston next week and that it's smart for Democrats to get the number of candidates down to a "manageable level."
"It’s interesting because there have been huge sociological studies done that when people have too many choices, they don’t make any choices. I don’t think the DNC is wrong to want to at least get it down to a manageable level," she added.
She would, however, love it if there were more "economically conservative" candidates on stage next week at the debate and is curious to see which, if any, will "catch more fire" and move up in the polls.
The Powerhouse Politics podcast is a weekly program with new episodes every Wednesday. ABC News Chief White House Correspondent Jonathan Karl and ABC News Political Director Rick Klein interview the biggest names and examine the biggest issues in U.S. politics.