Oh no, I don't think Sununu's going to lose because it's a federal race. I think Sununu is going to lose because he has a hard record of extremism now that Democrats can run on.
Of course, this all bets on the NHDP actually deciding to make his extremism an issue. Which they've failed to do so far (see: education).
Here's the thing: The Democratic Party is incredible at snatching defeat from the jaws of victory. They're the party who lost to Donald Trump once and almost lost to him again. They're the party that doesn't fight for what they claim to want. When you have one party that's fascist and one that's feckless, your country does not have a bright future.