Positing a theory here - This election cycle has been pretty much the worst , I don't even live in the US and I'm not a citizen of your fine country but it's all I hear about constantly. Even back in 2008 ,things only got really heated for the last few months before the big election day but this time it seems like I've been hearing about election related junk for 2 years non-stop.
I'm sick of it. So I can only imagine that the average American must be 10 times sicker of hearing about it all the time.
Trump is a bigot , an asshole AND most importantly a narcissist. He LOVES the publicity , good/bad/weird , it doesn't matter. His supporters are also clinically brain damaged so they enjoy hearing about him all the time. Who watches the most television ? Especially when most news channels spend all of their time reporting on something viewers want to hear about ? Trump supporters. So it's like this self feeding snake of stupidity constantly shitting into it's own mouth. So - of course the networks want to report that "hey Trump is actually maybe going to get enough votes to almost win but probably still lose badly but keep watching in case this changes". It gives them better ratings, people fearful of a giant baby leading their country into a new age of ignorance and oblivion will start watching hoping to hear some good news (ie - trump electrocutes himself to death with toupee straightener ) and trumptards keep watching to cheer for their champion.
What does all have to do with constant poll fluctuations ? well, if everything was reported straight forward and honestly , you'd merely hear some dry news reports about how Hillary will end up with a solid lead from the electorate and that Trump has basically no chance of winning. Trumps fanbase then won't be watching as much because the news won't do much and the fearful folks won't have anything to be scared about so they won't watch either. Lower TV ratings.
So , that brings us to the polls themselves, even when Hillary's support does fluctuate downward - the real culprit here is that Trump supporters and die hard republicans will still vote for their parties champion so they keep the Republican vote strong in polled states. Hillary has her support base (and I think just because of non white male support alone it's slightly higher than Trump can hope to get) but there are a number of 18-25 year olds out there partaking in their first or second election that want to vote for a candidate that really represents their values (like the green party , even if Jill Stein is an anti-vax crackpot). This vote has been fluctuating back and forth for months now because many in this group don't see Trump as a real threat , whenever they Do , they say "yeah I'll vote for hilldog" but then good polls come out and they say "eh, it's safe to vote on an independent because Hillary will probably win anyway".
So these minor fluctuations are being reported every 2 days, and anytime Hillary drops at all (even if it's that nebulous % measurement) , it becomes national news because that's basically what people want to watch for better or worse.
Really though, I just sit here from Canada looking southward , wondering what a normal election would look like right now - one where Jeb Bush was the candidate chosen to represent the republicans and the usual boring spout of debates and such occurred and Hillary still ended up winning when it was all said and done but I didn't hear about it 30 times a day.