This poll would seem to be an outlier till confirmed.
An interesting poll statistic is that GOP enthusiasm has passed Democrat enthusiasm 69% to 67%. Independents are at 56%.
Looking back to the 2016 polling in the Johnson/Feingold race, may shed some light. As you remember most polls throughout the year showed Feingold with a fair lead.
However, the last Marquette poll covering 10/26 through 10/31 showed tightening. Among 1,190 LV Feingold led 45% to 44%. Among 1401 RV he led 43% to 42%.
During the whole year only 3 Survey Monkey polls during the last 10 days showed Johnson with a 1 or 2% lead. Survey Monkey may have better reliability than some of realize.
Here is the link to the 2016 polling:
https://en.m.wikipedia.org/wiki/United_States_Senate_election_in_Wisconsin,_2016
