Both parties are doing their best to prepare for the May 22 vote-by-mail special election in Hawaii — but the winner-take-all contest is one of the most unprecedented and unpredictable in recent memory.

One of the key reasons the current state of play of the three-way race is more difficult to discern is tied to the challenges of polling in a relatively young and ethnically diverse state.

“People say their states are different and they are right, but Hawaii is probably the state that is more different than any place in the country and the most difficult to poll accurately than any other state,” said Mark Mellman, a Democratic pollster working with the Democratic Congressional Campaign Committee’s independent expenditure operation in the special election.

An internal DCCC poll published online last week by the Atlantic Monthly showed Honolulu City Councilman Charles Djou (R) and former Rep. Ed Case (D) tied at 32 percent, with state Senate President Colleen Hanabusa (D) at 27 percent and 9 percent of voters undecided. The DCCC did not confirm the poll’s authenticity and a date for the survey was not published; however, it’s clear that both parties are making decisions based on the numbers.

Several Democratic sources confirmed that the DCCC is supporting Case in the race, even though Hawaii’s two Senators are backing Hanabusa. DCCC Chairman Chris Van Hollen (Md.) did not deny that the committee is lending support to Case when asked about it during a Monday conference call with reporters.

“We are focused on exploiting the record of the Republican candidate in Hawaii,” Van Hollen said.

But pollsters both on the mainland and in Hawaii agree that the accuracy of surveys done in this race are very difficult to predict, given the state’s unique ethnic makeup, not to mention the balloting-by-mail component.

The biggest polling pitfalls have to do with the myriad ethnic groups in Hawaii, which also mirror the three leading candidates in the race. Only 19 percent of the people in the 1st district are white, while 53 percent are Asian and 14 percent consider themselves to be of two or more races. Case is white, Hanabusa considers herself Anglo-Japanese American and Djou’s heritage is Chinese and Thai.

Cultural sensitivity when doing surveys in Hawaii is so nuanced that one pollster commented that polling there is more like Japan than in any other part of the United States.

First of all, many survey participants —particularly Japanese-Americans — will say they are undecided when they are questioned about their voting preferences.

“And that’s not true,” said Dan Boylan, a political science professor at the University of Hawaii. “They just won’t tell a person with a disembodied voice on the phone how they’re voting.”

Japanese-American women, especially, tend to be underrepresented in polling because they decline to answer — a circumstance that Boylan argued could give Hanabusa an edge in the race.

“Let’s say there is 15 to 20 [percent] undecided, I would cut that in half in favor of Hanabusa,” Boylan said.

Local and national pollsters also agree that Filipino groups are often under-represented in polls because they live in larger households. Caucasians tend to be over-represented in many polls.

Secondly, Boylan and local pollsters agree that mainland pollsters are often too pushy on the phone and they may turn off many Hawaii respondents. Barbara Ankersmit, a Democrat who has been polling for 36 years in Hawaii, commented that mainland pollsters’ pronunciation of the often-complicated ethnic names can be way off the mark.

“One of the other real problems that mainland pollsters have here is pronunciation and not sounding local,” she said. “I think that gets them a higher refusal rate.”

Nonetheless, all three candidates in the race have hired mainland pollsters: Hanabusa has hired Anna Greenberg, Djou is working with the Tarrance Group and Case has hired Fred Yang, who appears to be the first mainland pollster Case has used in his bids for federal office.

On the other hand, Bob Moore, a GOP pollster who has done work in Hawaii, said that the Aloha State is no different from many others in that selecting a good sample is key to getting a good survey.

“The people who say it’s complicated are trying to keep others out or scare them away,” Moore said.

Hawaii’s political community also appears to have differing opinions about whether to use local pollsters or those from the mainland. While the party committees prefer candidates use pollsters with national experience, those on the island say it’s a bad idea.

“I would never hire a pollster from the mainland to poll in Hawaii,” Boylan added.

Candidates and operatives “either look at mainland consultants with suspicion or benign neglect,” said one Democratic pollster from the mainland. “You hope for benign neglect.”

There are other political customs that mainland operatives consider to be outdated.

Many politicians engage in a local tradition of “sign waving,” which involves candidates and their supporters waving signs on the sides of busy highways and highly trafficked intersections. This became a custom because it is illegal in Hawaii for candidates to post campaign materials on billboards and utility poles.

A mainland pollster said that survey data actually show that Hawaii voters hate this practice because it causes car accidents and creates an ugly distraction on the side of the road.

“Tell someone in Hawaii politics that sign-waving is not important, and they’ll tell you that’s crazy,” the pollster said.

Kathleen Hunter contributed to this report.