The Iowa Straw Poll, a Republican Party tradition since 1979 that was cherished by candidates vying to win the nation’s first nominating contest, is dead for the 2016 presidential cycle, party officials said Friday.

The move was made as candidates in one of the largest presidential fields in modern Republican history showed diminishing interest in participating in the August event, in which campaigns would spend lavishly to court local Republicans to emerge supreme in a poll at the carnival-like gathering.

“I’ve said since December that we would only hold a straw poll if the candidates wanted one, and this year that is just not the case,” Jeff Kaufmann, the Republican Party chairman in Iowa, said in a statement emailed shortly after a special meeting of the party’s state central committee.

The termination of the straw poll reflects a trend in Republican campaigning that began in the 2012 presidential cycle toward a contest waged increasingly on the stages of debates and in the confines of Fox News studios. The straw poll’s significance was diminished during that campaign cycle when its winner, Michele Bachmann, finished at the bottom of the pack in the caucuses, and its cancellation in 2015 suggests a nationalized nominating battle may have finally arrived as candidates focus less on early contest states.

The vote to end the event, which was to have been held in Ames, Iowa, was unanimous.

“I see this as entirely a candidate decision,” Mr. Kaufmann said in an interview, adding that many candidates and campaigns had urged the state party, in private conversations, to forgo the poll. He declined to name them.

Dozens of Iowa Republicans mounted a last-ditch effort to save the poll, gathering signatures on petitions and sending letters to the campaigns pleading with them to compete. One county activist even suggested that if a White House hopeful could not make his or her case to Iowans, they might not be able to confront the Islamic State. But once a handful of the top candidates said they would not participate, and were not going to be pressured to change their minds, it was clear that the event had to be ended.

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In 2012, former Gov. Mitt Romney of Massachusetts, the eventual Republican nominee, skipped the straw poll, and then-Gov. Rick Perry of Texas announced his presidential candidacy the day of the poll, knocking the wind out of the sails of Mrs. Bachmann, then a Minnesota congresswoman.

This year, former Gov. Jeb Bush of Florida said he would skip it, and others are more focused on husbanding resources to lift their standings in national polls to make the cut for the early debates, which are being limited to 10 candidates.

The move to cancel the summer rite will also come as a relief to Gov. Scott Walker of Wisconsin. He is leading in early Iowa polls and had avoided taking a position on whether to compete in the straw poll, not wanting to offend party activists but also concerned about the prospect of jeopardizing his standing by playing aggressively and losing.

The event offered an opportunity for lesser-known candidates to make a splash. In 2008, former Gov. Mike Huckabee of Arkansas won the caucuses after a surprise showing in the straw poll the previous summer. Yet despite the straw poll’s power to elevate, many establishment figures in Iowa have also resented it for years, believing it amplified the voices of the most conservative, and in some cases most fringe, members of the field.

The party decision, which came after cable television networks declared that a candidate’s standing in national polls would determine their participation in debates, illustrates how the power to winnow the Republican presidential field is flowing away from the states that traditionally played that role with their early nominating contests. Republican hopefuls who did not meet expectations at the summer gathering had often dropped out of the race before the caucuses were held early the next year.

“If there ever was a year that we needed an event to winnow the field, it was this cycle,” said Matt Strawn, a former state party chairman. “Campaigns should not view this as an excuse not to continue organizing throughout the summer.”