Why the 20-point spread in KSTP, Strib Minnesota polls? They’re BOTH outliers

What the recent Star Tribune and KSTP polls lack in coherence when placed together, they make up in symmetry: In both races measured, SUSA and PSRA are exactly 19 points apart in their margin spreads (McCain +1/Obama +18, Coleman +10/ Franken +9).

So what gives?