“Today, our beloved straw poll is under attack from political elites who want the people to have less power in the nomination process,” wrote Craig Williams, the Carroll County party chairman.

In his own email to a list of undisclosed recipients — also forwarded by an Iowa Republican — Mr. Williams used even more provocative language that underscored the nervousness party activists feel about the potential decline of the poll’s importance.

“All a candidate really needs this year is 1) a plane ticket to Iowa, 2) a hotel room for the night and 3) the boldness to face 20,000 Iowans,” wrote Mr. Williams, who is also a member of the state party’s governing board. “If they can’t do that, how can we expect them to face ISIS?”

The last-ditch effort to keep the straw poll relevant comes after a succession of candidates have stated that they would not spend money to bus in, feed and purchase admission tickets for supporters. Jeb Bush, Mike Huckabee and Senator Marco Rubio of Florida have said they would not try to win the straw poll, which takes place in Boone, Iowa, this year. Gov. Scott Walker of Wisconsin and Senator Rand Paul of Kentucky have said they were not sure yet whether they would spend money on the poll.