Remington is a Republican pollster the same way PPP is a Democratic pollster. Their final poll in 2016 actually underestimated Trump's winning margin and 538 gives them a mean-reverted bias of D+1.1, so the idea that we should just add 5 points or whatever to McCaskill's numbers because of the (R) is silly. Of course she could win, but I don’t get (or, actually I do) why people now think she’s much safer than Heitkamp, lmao. You should probably refrain from bashing Republicans for making "overconfident" predictions when you’re calling this Lean D and "unskewing" polls which don’t show her ahead.
I mean, the average of polls puts her only very narrowly ahead (thus why I'd rate it a Toss-Up), but the average of polls in North Dakota show Heitkamp slightly behind. So if you take the polls at face value, it's not at all unreasonable to assume that she could do better than Heitkamp.