DES MOINES, Iowa — Republicans in Iowa have opted to carry on with their presidential straw poll, a summer political tradition that detractors decry as a sideshow.

Despite criticism from some prominent Republicans, including Gov. Terry Branstad, the Republican Party of Iowa’s central committee unanimously voted Saturday to continue the event.

Committee members said the poll energizes the party base and serves as an important early test of a candidate’s campaign strength.

“It is indeed an opportunity for candidates that are lesser-known, with not nearly the financing that some candidates would have, to really have an impact,” said committee member Loras Schulte. “This is kind of the kickoff to the national election, if you will.”

Iowa Republican Party Chairman Jeff Kaufmann said the event will be held in August, but the date and location must still be determined.

First held in 1979, the straw poll has grown from a county Republican fundraiser stop to a large event on the Iowa State University campus, where candidates spend heavily to entertain supporters.

The poll has been a lackluster predictor of who will win the nomination. Its winners in 1979 (George H.W. Bush), 1987 (Pat Robertson), 2007 (Mitt Romney) and 2011 (Michele Bachmann) did not win the nomination. Only twice – in 1995 (Bob Dole, who tied with Phil Gramm) and 1999 (George W. Bush) – did the straw poll winner go on to win the nomination.

In 2011, about 17,000 people turned out – far fewer than the roughly 120,000 who voted in the January 2012 caucuses. Bachmann, a Minnesota congresswoman, spent $2 million on the event and won the poll, while Romney, the eventual nominee, chose not to participate.

Supporters of the poll say it is a way to gauge candidate strength early, while critics say it is a costly event that can have an outsized effect on the race.

A key question for 2015 is which candidates will choose to participate in the poll. If several candidates with more establishment backing opt-out, as Romney did in 2012, the poll results could be less meaningful.

The Republican National Committee provided the state party with an advisory opinion Thursday that said the straw poll appears permissible under new party rules, but the RNC stressed that the event is a fundraiser and the party must make clear that any vote is “unofficial and unscientific.”