Voters often don't feel sufficiently informed about a candidate, a race, or a referendum issue, and would rather leave those portions of a ballot empty instead of casting an uninformed vote.
While it's fine to abstain from voting or leave blanks on a ballot because you feel you lack knowledge, experts recommend that you do what you can to fill out an entire ballot. At the very least, they say, you should make a special effort to vote in the races and ballot issues that are likely to affect you directly: state legislature, city council, school board, and referendums that will impact where you live.
There are other reasons why people sometimes leave ballots partially blank. The 2016 presidential election featured two of the least popular leading candidates the United States has ever seen. Many voters left the presidential ballot blank as a “protest vote," a practice sometimes called undervoting. About 1.7 million people left the presidential election portion of their ballots blank in 2016.
But many caution against doing that as well, for the primary reason that whoever is elected president will appoint Supreme Court justices and push federal legislation that you might not like. In fact, after his electoral college win in 2016, Donald Trump went out of his way to point out how important non-voters were to his success. A handful of states were turned his way by these undervotes.
Also, if you wish to cast a protest vote, don't do so by defacing the ballot or by filling in a portion of it incorrectly. It likely will be classified as a spoiled ballot and won't be counted at all. And when a close race results in a recount, many states examine ballots closely to determine the voter's intent. Don't partially mark a ballot you don't mean to mark in full.
"Do I have to vote on everything on the ballot?" The answer to this question is no. But would you, if you were informed? Consider researching the issues and coming to the polls prepared.
Depending on where you live, there might be dozens of issues and candidates on a given ballot. It can be overwhelming to come up with an informed preference about each one.
To make the voting process simpler, there are resources that let you enter your zipcode and get a quick primer of the races and issues that are relevant to where you live. BallotReady lets voters compare candidates, including biographical data, where they stand on the issues, and from whom they've received endorsements.