The Reform Party’s write-in primary for Suffolk district attorney could end up involving far more than the 122 voters enrolled in the minor party.

A write-in race became a reality last week when Democrats filed more than the six signatures needed to wage what is formally known as an “opportunity to ballot.”

But unlike most political parties in the state, which permit only party members to vote, the Reform Party rule also allows those not aligned to any political party to cast ballots. That means that another 249,785 voters will also be eligible to vote.

The Reform Party designated Republican Ray Perini as its nominee, which means his name will appear on the ballot.

But the “opportunity to ballot” permits party members and those unaligned with a party to write in the name of Police Commissioner Timothy Sini, the Democratic candidate for district attorney, or anyone else they would like to see in the $193,133-a-year job.

However, the ballot line is not likely to be of much value in the general election since it is far down at Row H on the ballot.

It also creates an added cost for the county board of elections, which must print ballots to accommodate a 75 to 80 percent turnout no matter how many voters actually show up.

That means an added cost of $93,315 to $99,882, since elections officials say each ballot costs about 50 cents.