In this Aug. 13, 2011 file photo, Republicans enter the Hilton Coliseum before casting their ballots in the Iowa Republican Party's Straw Poll in Ames, Iowa. (AP Photo/Charlie Neibergall, File)

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The Iowa straw poll, a political jamboree that has been a fixture in the Republican presidential nominating process for nearly four decades but has come under criticism in recent years, was cancelled Friday by state GOP leaders in a unanimous vote.

The Republicans cited a lack of interest in the event from leading presidential candidates and they said their decision will help preserve the importance of the Iowa caucuses, which are slated to be held early next year before any other state gets to vote.

"Many candidates are still concerned about participating in an event that carries significant media-driven expectations well ahead of our First in the Nation Caucuses," said Iowa Republican Party Chairman Jeff Kaufmann in a statement. "While we still deeply believe that the Straw Poll offers a fantastic opportunity for candidates, we need to focus on strengthening our First in the Nation status and putting a Republican back in the White House."

The move marked the official abandonment of a non-binding poll weighed down by expensive costs and a growing belief among Republicans that it held little predictive value. It means an already-packed and wide open field of GOP hopefuls will be subject to one less major benchmark on the road to 2016.

While representatives for seven candidates and probable contenders dropped by a straw poll planning session last month, no one from the top-tier campaigns was there.

Jeb Bush and Mike Huckabee -- who won the 2008 Iowa caucuses -- were opting out. Sen. Marco Rubio (Fla.) had signaled that he would not participate. And Wisconsin Gov. Scott Walker, seen as an early front-runner in Iowa, had been non-committal.

"I went to my first caucus in Dexter, Iowa when I was 13 years old, and I love the straw poll," Brenna Bird, a member of the GOP state central committee, in an e-mail. "But, every presidential election year is different, and this year, despite our best efforts, we did not have enough candidate participation for a successful straw poll."

The straw poll is an Iowa political tradition that dates back to 1979 and served two basic purposes: raising money for the Iowa GOP and showcasing the presidential candidates and their relative strengths months ahead of the caucuses.

But the summertime event faced an existential crisis as Republican strategists and officials questioned its utility in predicting how hopefuls will fare in Iowa and whether it's a worthwhile investment of candidate time and money. In 2011, then-congresswoman Michele Bachmann won the straw poll; she went on to finish last in the 2012 caucuses.

It had also become expensive to compete in the poll. Candidates have had to pay for plum spots at the event, which has been likened to a county fair or a carnival. Hopefuls had to shell out big bucks to transport supporters and pay for food.

Iowa Gov. Terry Branstad (R) has been one the poll's most prominent critics, once saying the gathering had "outlived its usefulness." The emerging crop of White House hopefuls also showed little interest in the event.

The decision to cancel the straw poll could help Walker, an all-but-declared candidate whose Midwestern roots and conservative resume have made him popular among Iowa Republican activists. Participating in the event would have been a high-risk, low-reward proposition for him. A strong showing would have only validated his position at the front of the pack; a weak one would have set off concerns that he was in trouble.

"He clearly didn't want to participate," said Craig Robinson, a former Iowa Republican Party political director. He added: "I expect him to really ramp things up in Iowa now in terms of on the ground stuff."

Longer-shot candidates like Ben Carson and possible contender Donald Trump stand to lose the most from the absence of a straw poll, said Robinson, since they are looking for a platform to elevate them in the campaign.

Even as the effort to scrap the straw poll picked up steam, many Republicans rallied to try to save the event. In May, 156 state Republican activists took to the pages of the Des Moines Register with an op-ed urging candidates to participate.

And in January, the state GOP central committee voted 16 to 0 to begin planning a straw poll. This year's version had been slated to take place on Aug. 8 in Boone instead of Ames, where it has been held in past years.

While Republicans see the cancellation of the straw poll as a necessary if difficult step, they contend that it won't stop them from getting to know the many candidates for president, since they will have plenty of chances as they barnstorm the state in the coming months.

"I still look forward to meeting candidates as they campaign in my community," said Bird, the Republican activist.

Jose A. DelReal and Jenna Johnson contributed