Riverhead officials are weighing a ban on political party leaders serving in elected posts -- a proposal that has deepened a rift between the town's Republican supervisor and the GOP chairman after a divisive nominating convention last month.

Riverhead Republican chairman Mason Haas, who also serves as elected assessor, would have to forfeit one of his roles if the bill passes. He said he believes he is the target of the ban because he is the only official it would immediately affect and he has had a fraught relationship with Town Supervisor Sean Walter, a fellow Republican.

"It's most definitely a personal vendetta," said Haas, who has led the party since 2013 and has served on the three-member board of assessors since 2007.

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But Walter, who first proposed the ban two years ago, said it is a good-government practice meant to prevent party officials from consolidating power. The law would block the four executive members of any town, county, state or national party from serving as elected officials.

"People, when they go into certain offices, you want to make sure that they're above any kind of political reproach," Walter said. "You don't even want a faint hint of an appearance of impropriety. The fact is, the executive committee and chairmen of various parties wield immense political power."

Walter, who has been supervisor since 2010, lost the GOP nomination to Councilwoman Jodi Giglio at the party's May 26 convention and is waging a primary. Haas is backing Giglio.

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Walter said the bill -- which has never come up for a vote -- is not payback for his convention loss, but said proposing the ban two years ago may have contributed to him losing Haas' support. Haas said that's not true, and he supports Giglio because the town needs a businessperson at the helm. Walter is an attorney.

Giglio said she believes the proposal is a result of a personal dispute between Walter and Haas, but added she supports a hearing because it would give the public an opportunity to weigh in.

The Riverhead Town Board, which consists of five Republicans, voted unanimously on June 16 to schedule a hearing Tuesday on the proposal. If it passes, Haas would legally have 20 days to resign from one of his posts. But Haas said he would not step down from either one.

"This is politically motivated to take away the constitutional rights," he said. Walter said he would prefer an expanded ban that blocks all political committee members -- not just executive members -- from serving in elected posts, but that idea lacked support on the town board. Ethics laws governing the activities of political leaders vary widely across Long Island. Riverhead's proposal is similar to Brookhaven's 2011 law, which bans a political executive committee member from serving as an elected official, "bingo inspector" or member of various appointed boards.

Since 2004, Southold has banned even general members of a political committee from serving as elected officials. Islip and North Hempstead have no laws preventing party leaders from serving in elected posts, officials there said.

In 2013, Southampton Town officials barred police officers from serving on political committees.

With Carl MacGowan, Sophia Chang and Scott Eidler