Many people have well thought out reasons for not voting in presidential elections (some still vote only in local elections or for/against ballot initiatives). This blog post compiles several given by libertarians. Here are my responses to the general themes I see:
Voting, even for a hopeless candidate that aligns most closely with my beliefs, is only a perpetuating endorsement of the hopelessly broken and immoral system.
If the government is the crew of an enormous ship horribly mismanaged and sailing in the wrong direction, despite your best intellectual justifications, inaction does nothing to sink it, redirect it, stop it, or even wound its feelings. Even if you oppose the system completely, voting is the only direct influence you have on it. Every four years one of two imperfect and corruptible people will be captain, and the worse of the two will harm more lives than the other. The very least you can do to mitigate this is to suggest the least harmful choice according to the best information available to you. You don’t have to tell anyone for whom you vote (or that you do), nor can any reasonable person claim you owe any responsibility for another’s actions.
Any positive action you do personally has much more effect than the act of voting.
You can support nearly any inaction based on the weak assumption that the opportunity cost of acting is too great; due to spending your time voting you could not perform one additional good deed. The fact is you can send in an absentee ballot and still have time to (and should) call mom, do good work, help the needy, educate fellow citizens on important issues, and, depending on your mania, begin your move abroad or work on your plan to throw yourself in the gears of the system. Voting doesn’t prevent you from doing any of that.
In my location, my vote is statistically useless to exert change.
This justification definitely carries the most weight with our system, but dissenting votes still give evidence of opposing voices and pool to show opposition on a larger scale. Obama was an electoral vote landslide, but 47% of voters preferred someone else. Only with such dissention can you remind people that no presidential vote should be considered a mandate to support the winner’s policies. In any country where votes are actually counted (we’re lucky we’re in one), you have some non-zero influence in steering the ship. Calculus shows even infinitesimally small numbers add up.
Also, while so many, no doubt, vote based on misinformation, misunderstanding, or even without putting much thought into it, we desperately need critical thinkers and the well-informed to vote.
The French 2002 presidential election is a pretty interesting study of what can go wrong in a direct election. The left wing had splintered so much that the run-off election presented two right wing candidates; leftists called it a choice between a crook and a fascist. Frustrated voters chose the crook by a landslide, but some suggested voting for politique du pire (“politics of the worst”) in hopes that the resulting bad governance would build sufficient outrage to fuel reform. Maybe the presidential system itself is flawed and all reforms will always lead in circles towards or away from more direct elections.