The intent of the letter is obvious.  The message within the letter speaks to exactly what mindset the modern Democrat party holds:

I think the Democrats just threatened me: pic.twitter.com/wGvYInosk5

— Jonathan Coulton (@jonathancoulton) October 30, 2014

(New York Post)  Democrats are telling voters that they had better head to the polls — or else.
The New York State Democratic Committee is bullying people into voting next week with intimidating letters warning that it can easily find out which slackers fail to cast a ballot next Tuesday.
“Who you vote for is your secret. But whether or not you vote is public record,” the letter says.
“We will be reviewing voting records . . . to determine whether you joined your neighbors who voted in 2014.”
It ends with a line better suited to a mob movie than a major political party: “If you do not vote this year, we will be interested to hear why not.”
The letter and accompanying post card was criticized even by party members, with one Democratic consultant saying it was the wrong way to inspire votes.
“It’s a threatening letter. It’s a scare piece that is unnecessary and inappropriate,” the insider said.  (read more)
Sounds a little alarming, but actually it’s just typical.  MSNBC Alex Wagoner spoke to the mindset of modern Democrats, when she shared that all means are justified by the ends.

[…]  Wagner concluded the segment by saying that it shouldn’t have to be the kind of threats contained in these ads that get people to vote, “but if it does, so much stronger the party is for it.”…. (link)