Both are standard now — but only one is old
"Sneaked" and "snuck" are both accepted past tenses of sneak in American English. Sneaked is the original, regular form, built like walked or talked. Snuck is the newcomer: it first shows up in print in the late nineteenth century, as a dialect form, and has since climbed all the way to standard status. Merriam-Webster's usage note describes exactly that journey. In everyday American speech today, snuck is extremely common, and for many younger speakers sneaked sounds stiff or even wrong.
Which is what makes this vote interesting: it captures a grammar change in progress, before it is finished.
A verb that went irregular
Most English verbs travel in the other direction. Over the centuries, irregular verbs tend to become regular: helped replaced holp, climbed replaced clomb. Snuck is a rare case of a regular verb picking up an irregular past, and linguists find it fascinating for that reason.
The model is easy to spot. English has a small family of verbs whose past tense uses the same vowel as snuck: dig, dug; stick, stuck; strike, struck; sting, stung; swing, swung. Sneak sounds close enough to these that speakers pulled it into the group. Dragged and drug, dived and dove show the same pull, with mixed success.
An American story, mostly
Snuck began in the United States and remains more American than British. It has been spreading in British and Canadian English as well, but more slowly, and British style guides are generally more reluctant to accept it. In the United States, by contrast, it has long since left the dialect label behind and appears freely in newspapers and novels.
Some usage guides still prefer sneaked in formal writing, and editors divide on the question. But the old charge — that snuck is uneducated — is hard to sustain when educated writers use it constantly and the dictionaries record it without a warning label.
What your vote reveals
For a lot of people, this question has no right answer, only a familiar one. Try finishing this sentence without thinking: "Last night, the cat ___ into the kitchen." Whatever came out first is the form your grammar has already chosen.
If snuck wins clearly, the tally will confirm what the dictionaries have been describing for years. If sneaked holds up, it will show that the older form still has real loyalty, at least among people who care enough about grammar to vote on it.
Sources: Merriam-Webster entry and usage note for "sneak"; histories of irregular verb change in English; usage guidance in American and British style manuals.