am I understanding correctly that you're suggesting that an Iowa poll was artificially made to favour Harris in order to get more people to vote for her?
Yes. People naturally like to vote for winners, and those who look like winners.
There was *massive* news coverage of the Selzer poll's surprising result, with accompanying breathless commentary discussing how this was proof that hordes of Republican women were indeed secretly[1] voting for Kamala. Cue the tens of thousands of Redditards' comments on how Harris would surely win not just Iowa but Texas, Florida, Ohio, etc.
[1] For example, the Julia Roberts-starring TV ad <https://www.youtube.com/watch?v=FaCPck2qDhk> showing how women could and should secretly vote for Harris and not tell their horrible husbands.
(Beware; the cringe level is so overwhelming that if your brain doesn't shut down in self-defense your computer might explode. There is a reason why the ad is not linked directly anywhere on Reddit except a handful of posts with a half dozen comments. If Redditors saw it as truly "stunning" and "brave", it would have been reposted 100 times, each time with 20K upvotes and 3.5K comments.)