What I think is happening here (re: Heitkamp) is either:
a. She's serious about taking the position
or
b. Bannon and co. struck a deal with her that would entail Heitkamp being publicly considered for a cabinet position by Trump, which would give her bipartisan credibility in 2018, in exchange for her vote to confirm crucial cabinet positions.
Her vote's not needed for that. The Republicans have all the votes they need. That said, even if she were to stay in office and win reelection, I think the Senate will remain in Republican control in 2018. There are so few Republicans up in the class of 2018 that at most the Dems can gain only 1 barring an absolute disaster in the next two years, in which case they might regain North Dakota anyway.If she were to take such a position, I'm wondering if that'd be a tell that she views her own reelection prospects to be quite dim. Some people are writing her off for reelection. I'm not one of them, since North Dakota is a small state where retail politics matter. However, she would probably have more insight into her own prospects than anyone. If she did take the position, it'd still be nice if she managed to get the Governor to appoint a moderate Dem replacement (like when Democratic Governor Lynch of NH would have appointed a liberal Republican caretaker if President Obama had nominated Judd Gregg to Commerce).