I don't think Donnelly will do better than Brown, but I believe Tester and Heitkamp (and Manchin, assuming he faces Morrisey) are in a better position to win reelection than Brown and maybe even Baldwin and Nelson.
I'm sure that I'm allowing my personal affinity for Donnelly to cloud my objectivity, but Donnelly has a few things going for him that some of the other Midwestern targets (Brown, Baldwin, McCaskill) don't: 1) Donnelly is easily the most moderate of the bunch and is overall a better fit for his state; 2) he has the lowest national name recognition and profile, which I would consider helpful in countering the inevitable ads tying him to the DNC, Schumer, and/or HRC; 3) he's taken a lead and touted his (bipartisan) achievement in a number of Indiana-specific legislative initiatives, not the least of which includes combating opiod abuse; and 4) he's a genuinely skilled retail politician (Sherrod is too, of course, but Donnelly doesn't get enough recognition for his skills).
Like I said, I like Donnelly personally and politically, so it's difficult for me to be objective, so please take the above with healthy skepticism.
And to the topic at hand, it's dangerous to dismiss a poll simply because the result isn't what one wants to see. Brown could very well be in trouble.
