Trump Midterm, buyers remorse
I know this is what Democrats will say from now on until November 2018, but it still doesn't change the fact that Baldwin will be seriously challenged, especially with Walker and other statewide Republicans running for reelection. She is not some unbeatable popular titan, and the GOP would be insane to ignore an opportunity like this.
These early polls don't tell us much at this point in time, I've said that in the Nevada thread as well.
No... it will be competitive, but look at Feingold/Michaels 2004 as an example of what I think this race will eventually pan out to be, especially as more electable GOP candidates decide to take a pass, hold their safe seats.