SourceGaming is looking into post-ballot popularity at the moment IIRC, and said that K. Rool was still top 5 over there based on early research.
If only because of timing, I don't think Isaac's Smashified will help him out much for the ballot. Early on, K. Rool had the designation of being one of their first characters, their first first party character, and released alongside other widespread news pieces like "Playtonic Supports K. Rool for Smash." Now, however, I think people are burnt out on Smashified (it has several thousand fewer upvotes on Reddit from the Banjo one, only a few dozen now), partly because of how many times they push artwork releases back, partly because they try to act coy and tease new releases in a Sakurai kind of way (one is enough for anyone), and partly because it's a less exclusive "club" now, so to speak, with way more third parties and even OCs getting chosen before requested first parties.
In general, I don't think anyone is going to make any big last minute surges in the ballot, it's more just a matter of whether the big contenders can keep their momentum in the home stretch and not fall behind. We have about six weeks left to keep up ours before we can rest at last and await an outcome.