Come Christmas Eve, you will find thousands of frantic Santas dashing through the aisles, grabbing boxes at random and snapping at one another. Come Halloween morning, we create long lines, waiting to run through the costume store. All year, we knew the date. We had seen ad after ad, and it was circled several times on our calendar.

But here we are, nonetheless.

Why does this always happen? Is it that we start too early? Halloween came to the stores months ago, bumping into the Fourth of July as it entered. Christmas is arriving now, before Thanksgiving even gets a foot in the door. We have had months and months (and months) to see all our options and grow tired of them. And then the deadline arrives, and we go into a panic, tearing everything we can reach off the bare metal shelves.

We arrive home and stare at the six sets of My Little Pony Friendship Is Magic Accessories that, in our deadline-addled frenzy, we seemed to think would make appropriate holiday gifts for our entire families.

What hath the deadline wrought?

So why should it be any different with the election? That, we’ve been hearing about for years. It feels, now, that these candidates have always been with us. Fatigue doesn’t begin to describe it. This election jumped the shark months ago, when Newt Gingrich was bitten by a penguin. Now it feels like we’re in reruns.

Still, a lingering percentage of us still haven’t made up our minds. The difference between the 48.56 percent of likely voters leaning toward President Obama and 48.49 percent headed for Mitt Romney in the most recent Washington Post-ABC poll is — a few procrastinators.

Welcome to Procrasti-Nation.

What makes a procrastinator? This should be easy to determine. I am one myself. To quote Douglas Adams: “I love deadlines. I love the whooshing noise they make as they go by.” I tried to make a list of things that define the true procrastinator. Here is the list.

1. Some things are hard to procrastinate on — removing pies from ovens, extinguishing fires, being present for your children’s childhoods, ending World War I, just to name a few. Once I procrastinated on breaking up with someone and we wound up in a six-year relationship by mistake.

But most things don’t work like that. You can procrastinate almost indefinitely, and the outcome is not noticeably different. Take this piece, for example.

Which kind is the election?

Procrastinators come in several stripes. There are the ones who are constantly aware of what they are supposed to do but think they still have enough time to do it. There is a certain arrogance to these procrastinators. “This will be very easy,” they say. “I don’t need to worry about that, because I could do it in my sleep.”

They believe that the eleventh hour will show them forth in all their greatness, that inspiration comes just as the clocks sound midnight, that they will snatch victory from the jaws of defeat, the way Kiefer Sutherland used to do during Hour 23. (I assume. “24” is on my list of Things to Watch.)

Then there are the ones who completely forgot this was due today and are frantically scribbling to beat the band. They are not procrastinators by inclination. It just slipped their minds.

And there are the ones who meant to do it, but the longer they contemplated the task, the more mammoth it got. They are just going to throw darts at it and hope it works itself out.

How does this factor into the election? Who still hasn’t decided? When will they decide? How? By taking an online quiz about Whose Politics Match Yours the night before? In the line, jostling between Those Old Ladies Moving Very Methodically Who Always Show Up When You Have Somewhere Urgent To Be? In the booth? Once they see who falls first alphabetically on the page? (Laugh if you like, but the Democratic Party says this happens in Tennessee.)

Why are we so startled at the Voter Procrastinator when we’re surrounded by procrastinators in everything else? After all, this isn’t new. The same last-minute scramble happens every four years.

If it weren’t for the last minute, as someone wise once quipped, nothing would ever get done at all.

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Alexandra Petri is a member of The Post’s editorial staff.