I've not seen any reporting that stated it was publicly available polling data. It was stated as polling data from the Trump campaign that Manafort would have access to as the campaign chairman.
It would also make little sense for interaction with Manafort since Russian operatives could get publicly available polling data information themselves.
The value of working with Manafort and the Trump campaign would be to get polling data not publicly available that could help them target states/audiences to hurt Clinton and help Trump. Cambridge Analytica anyone? This could include voter suppression strategies in key states against minorities and peddling propaganda to voters that may be open to voting for Trump.
This is also not the only evidence of conspiracy - we have 16 people in the or related to the Trump campaign who had interactions with Russians before, during and/or after the election. We have the Trump tower meeting with Russians and Manafort, Don Jr and Kushner to get dirt on Clinton. We have Roger Stone and other cronies interactions with Wikileaks, Guccifer 2.0 and Julian Assange, including foreknowledge of hacked material releases etc. We also have the Trump Tower Moscow project Cohen was working on with Trump and family members during the election as the Russians were actively attacking our Republic. None of them ever reported anything to the FBI and all of them have lied about their activities with Russia.
The other reporting that reinforces this coordination is that the Trump campaign and alt right media in their social media and messaging were echoing, amplifying and distributing the same or similar propaganda to achieve the same goals.
This has not stopped to this day; Trump just recently has peddled Russian propaganda about the 1989 invasion of Afghanistan, fake news about "incursions" into Poland by Belarus and the situation in Montenegro. He also famously stated Crimea was Russian because everyone who lives there speaks Russian. I hope Canada gets ready to be occupied by us since everyone there speaks English.
Do not forget also Trump's avid approval of Putin's idea to have Russian investigators work with the Mueller team to help figure out what happened during the 2016 election and the related despicable "offer" by Putin that all he would ask in return is to have American citizens on his enemy's list be sent to Russia for investigation of their crimes. The fact Trump agreed publicly this was "a great idea" and that he actually considered following through is beyond outrageous, cowardly and un-American.
Is Trump simply an idiot easily manipulated by the Russians? I would say yes, but it could be even worse than that and every American, regardless of party or anything else, should care very much about getting answers to that and every other question about his words, behavior and actions.