Seems weird that Smith would've lost 3% out of nowhere, so their old poll or this poll are probably off, if not both. Likely D.
Margin of error.
Also this race isn't getting much attention even locally. The local GOP seems to be using their strategy of raving about Ilhan Omar over and over which I have no doubt will be as successful as their "rave about Keith Ellison endlessly" strategy in 2018 (hell at least Ellison was running for a statewide office.) Also since Smith won pretty easily just two years ago she's both a known quantity and uncontroversial.
I think Lewis and the GOP were just banking that Smith couldn't win the same year as Trump winning the state. Now that it's clear Trump won't win they're scattering on the race an ld instead throwing resources at Collin Peterson (a hollow victory since that seat will be dismantled next cycle anyway.), protect their incumbents and a probably futile effort to save their State Senate majority.