So 4 of the recent polls showed Trump leading. 2 of the 3 that Trump lead, it is close enough to be a tie. I guess this meant Monmouth where Carson leads by 8 is a huge outlier in this case.
I think these 4 were post debates. Though, the jury is still on Gravis if that was post debate or not. 8/31 or 8/26. But yeah.
Before debate, Carson leads in every poll. Except for YouGov where it is a tie.
So the trend is, Trump had caught up to Carson's lead.
A good summary however a small lead of a few points is not really of much significance this far from the actual polls. The trend towards Trump is perhaps more telling but we need to see if it continues.
Overall the big picture is Trump and Carson significantly ahead of Rubio and Cruz who are ahead of the rest. So these four are looking to be the best chances to win Iowa.