She’s voting no because she saw the polls showing that she is going to lose badly so she might as well let the mask down and vote like extreme Lib that she is.
She plays the nice lady shtick to the hilt. Even with the statewide elections she has lost, she comes back and wins the next one by playing on public sympathy. About 15 years ago, she was able to add "breast cancer survivor" to her shtick. Long story short is that she is a political animal and North Dakota voters are finally waking up to that fact.
The other thing working in our favor here is that oil prices are heading up and, as a big oil producing state now, North Dakota voters like the earned wealth of oil revenue more than the former favored method of looting via government pork . . . which was always worth an extra 10% of so of the vote to candidates for federal office like Heitkamp. Democrats have a well-deserved image of being better porkers.