Etika's poll is unlikely to impact many votes in the actual Smash ballot, since the ballot ends in two days anyways. However it's not inconceivable that it could swing some last minute votes if Etika puts out a video on the top 5 ballot characters today or tomorrow. Since putting in a vote and sharing the link with Shantae supporters only a couple of seconds anyway, I'd say it's worth the time to do so for that reason alone.
Sakurai and Nintendo will be looking primarily at results from the official Smash ballot, so after October 3 we can basically consider the task of campaigning for Shantae to be finished. After October 3, the deluge of character polls will subside, making and sharing Shantae fan art will be just for fun, and there will be no need anymore to respond to every moron on the internet who decides to publicly badmouth Shantae.
That being said, Sakurai and Nintendo will still notice community opinions outside of the ballot to at least some extent. They take notice of community opinion on other matters, after all. Etika's poll and videos are probably not going to be the difference maker for who gets into Smash, but they are a non-trivial part of all the peripheral information available to Nintendo on community preferences.
Let's put it this way: you have to imagine that Sakurai and some other bigwigs are going to sit down in one or maybe a few different meetings and look at what data they have compiled from the ballot. They will go through a decently long list of characters and discuss briefly the pros and cons of each character, and whether they are worthy of more careful consideration. Those brief little conversations are going to decide the fates of most of the ballot characters. You add in an Etika poll here or there, and that could be enough to cause somebody sitting in that meeting to say something along the lines of: "also, community interest in this Shantae character appears to have continued its upward trend since the close of the online ballot." That could matter a lot, and that's why it's worth getting as many backers as possible to vote in this Etika poll, even though the ballot is about to close.
Speaking of Etika's poll, here's the current top 5, compiled from across all three of his polls:
1. Snake 4370
2. Shovel Knight 3908
3. Banjo-Kazooie 3571
4. Shantae 3342
5. Inklings 3213
The only change in placements is that BK and Inklings swapped places, with Shantae surpassing Inklings to stay put at 4th place in between them. Also the votes are slowing down now across the board.
GoldLiger
mentioned that there are around 20,000 backers for HGH. If we got even just 1-2% of them to put in a vote for Shantae in Etika's ballot, then Shantae would shoot up to #3, which would be seriously awesome. 5% of them voting would put her in first. I wonder if maybe WayForward would put out an update on their HGH kickstarter page asking backers to vote in the poll? Not sure how else to dig up more Shantae voters. It would be nice if we could just reach out directly ourselves.
.... Question for you guys: why all this distaste for Etika? I don't watch him regularly or anything, but he seems pretty inoffensive to me. Shouldn't we just be happy that such a well-known YouTuber has a soft spot for Shantae?