The Optimus poll is a robocall poll - not very reliable methodology overall (Rasmussen used to do robocall polls). Also, I can’t find much of a track record for the company to judge by. That may be why most people don’t pay a lot of attention to it.
The Marquette poll is supposed to be the premier poll for Wisconsin politics.
With such a large sample size I think it is probably more accurate than you think. The Marquette poll MOE is enough to be close to the Optimus poll, if the error is in Trump’s favor. And, neither poll measured the democrats or Independents who may vote...most likely for Trump. We shall see what happens Tuesday and I will either pat myself on the back or kick myself in the ass for what I just wrote...
The Marquette poll is only Republican likely voters.
Wisconsin is an “Open” primary state - which means that Democrats and independents can vote in the Republican primary. Trump has lots of Blue Collar Democrat Union supporters and independents and Wisconsin has many union workers.
Cruz may be ahead of Trump, but it is a lot closer than the 10 point spread this poll suggests.
A more accurate poll would be of everyone who is likely to vote in the Republican presidential primary, not just Republicans!!!
Not with a "margin of error of 5.8%".