Ivanka and Eric Trump recently experienced a rude awakening: They can’t vote for their father in Tuesday’s primary election.

They want to, but New York election law prevents them from doing so. This Election Day, untold numbers of New Yorkers will suffer the same fate when they walk into poll sites across the state to discover that they, too, are ineligible to vote in the presidential primary.

Why?

Because in New York, we don’t just have a closed-party system in which only enrolled Democrats and Republicans can vote for their respective candidates: The primary is closed shut. The deadline to switch parties or change affiliation is the earliest in the country — this cycle it was Oct. 9, 2015. If you’re a Republican, Democrat or unaffiliated voter, you’d better know six months out whom you’re supporting, because there won’t be an opportunity to reconsider.

This system both reinforces partisanship and punishes independent-minded voters, effectively disenfranchising them.

Participation is the basic test of democracy, and free and fair elections are necessary to legitimatize the people’s choice of representative. Usually in presidential politics, a clear front-runner emerges earlier in the calendar, making the New York primary perfunctory. But this year, despite the fact that the majority of states have already voted, there is no clear nominee in either party. New York matters.

In a state stacked with delegates, New Yorkers have an opportunity to change the race for the first time in 25 years. However, 3 million voters who aren’t registered Democrats or Republicans — 27 percent of all registered New York voters, including unaffiliated voters — will not be eligible to vote. And the multitude of “party switchers” will be left out, too.

What’s worse is that many of these voters who registered a change with the Board of Elections after the deadline think that they’re eligible to vote today. That’s because the New York Board of Elections sends out a notice acknowledging a change of registration that lists a person’s current party in big bold letters, and at the bottom in small print a person’s “Future Party” next to a cryptic caveat: “Effective Date November 15, 2016.”

Unfortunately, the “future” doesn’t mean the next election but the one after that. This will wreak havoc on Tuesday when these voters find out that they cannot vote in the primary election for which they thought they had successfully registered. Although they can try to vote by filling out a provisional ballot, it’s unlikely to count.

And if they need or want to contest their vote for whatever reason, they can’t because under the law only parties and elected officials have standing to do so.

Is it any wonder that New York, the third-largest state in the nation, ranks 49th in voter turnout?

New York’s registration requirements rob New Yorkers of their full democratic rights.

There are many different solutions to this problem. New York is one of only 11 states with closed primaries.

Eleven other states have open primaries in which members of either party can vote freely for any candidate regardless of party affiliation.

Twenty-four states have a hybrid system, with some variation between open and closed primaries for handling unaffiliated voters and changing registration. Eleven states plus the District of Columbia have same-day registration, allowing unregistered and unaffiliated voters to show up on Election Day and participate. Similar legislation is withering on the vine in New York.

At a time when so many people feel ignored by the political “establishment,” many voters prefer to remain unaffiliated rather than conform to a party label. New York City residents in particular are a transient population and many will go to the polls with their expectations set by their experiences in other states.

Simply fixing New York’s retrograde primary rules would be a start, but it isn’t enough. A modern mobile society with a 24-hour news cycle needs one uniform set of rules for registering voters, including same-day

registration, that apply equally across the country.

Susan Lerner is executive director of Common Cause/NY.

