FiveThirtyEight dismisses "A lot of what looks like momentum in the polls" toward Republicans (previously, toward Democrats) as "just random noise" and, oddly, mentions only in passing the election's "fundamentals" (which are atmospherics, such as a president's popularity).
I'm going with fundamentals and that sense of Republican momentum, as my earlier post--this morning--probably already suggested to you. It just feels creepy out there. When Joni Ernst can gain ground despite her gun-totin' lunacy, for example, then to me, the fundamentals swamp the statistical "noise."