In an attempt to curtail voter fraud, Miami-Dade commissioners made a small but potentially significant change Tuesday, deciding that the county should pre-pay return postage for absentee ballots — a measure first suggested by a grand jury nearly 15 years ago.

But the move comes with a caveat: The county will provide prepaid postage on return envelopes only for countywide elections, not for stand-alone municipal elections.

That fine print means cities that hold their elections separate from the county will have to decide whether to pre-pay the postage themselves, in addition to the election costs they already incur.

Elected officials in two cities, Hialeah and Miami Lakes, have already signed off on pre-paying return postage. Most others, however — including Miami, the county’s largest city — have yet to even consider the idea.

The prepaid postage proposal was recommended by a grand jury in 1998, after the courts ruled that a notorious Miami city election the previous year had been tainted by absentee-ballot fraud. Prepaid postage, the grand jury said, could prevent ballot tampering.

Voters currently must provide their own postage to send in absentee ballots, though the postal service will still mail the ballot if it lacks sufficient postage, and charge the county the difference.

The county has estimated that it would cost about $170,000 to pay for return postage for absentee ballots in a general election. Mayor Carlos Gimenez had said he was prepared to set that money aside administratively, without a commission vote, if the board had not acted on the item Tuesday.

The prepaid postage will be provided beginning in the Nov. 6 general election. Absentee ballots for that election will be mailed in mid-October.

On Tuesday, Miami-Dade Commissioner Jean Monestime suggested the county require all cities to pre-pay postage, but it was unclear if the county legally has that power.

The county measure, put forth by Commissioner Esteban “Steve” Bovo, was approved unanimously with a voice vote. Chairman Joe Martinez and Commissioners Lynda Bell, Dennis Moss and Xavier Suarez were absent for the vote.

Bovo’s proposal came after his office was embroiled in one of two ongoing Hialeah absentee-ballot fraud investigations that resulted in the arrest of two ballot brokers, Deisy Cabrera and Sergio Robaina. They have been charged with voter fraud and with violating a county ordinance that prohibits the possession of multiple absentee ballots.

Brokers sometimes visit voters’ homes promising free stamps for absentee ballots, but in the process, some have been accused of influencing the voter or even filling out their ballot.

Bovo’s former aide, Anamary Pedrosa, told prosecutors that Robaina and other brokers known as boleteros dropped off ballots at the commissioner’s Hialeah district office for her to take to the post office. Bovo has not been implicated in the probe.

Cabrera, who was charged in a separate case, has pleaded not guilty. Robaina has said that he did not fill ballots against voters’ intentions, as police say he did.

“Would it eliminate all the fraud? No,” Bovo said of his measure. “But there’s a chance for us now to give, first, peace of mind to the voter that requests the absentee ballot.”

His comments came after Miami Lakes Michael Pizzi, Hialeah Mayor Carlos Hernandez and Hialeah Council member Paul “Pablito” Hernandez (no relation) urged commissioners to approve the measure and to allow their cities to pre-pay postage for municipal elections.