(CNN) - Dino Rossi holds a large lead over two other Republican candidates in the battle to challenge Democratic Sen. Patty Murray of Washington, according to a new survey.
An Elway Poll of registered voters in Washington state indicates that 43 percent back Murray, who's bidding for a fourth term in the Senate, in the state's August 17 primary.
Thirty-one percent support Rossi, with fellow Republicans Clint Didier at five percent and Paul Akers at two percent. Seventeen-percent were undecided. Washington is the only state in the nation to hold a non-partisan primary, with the top two vote-getters advancing to the general election. Earlier this month California voters passed a referendum that would move the Golden state towards a similar system.
Rossi, who announced his candidacy last month, is arguably the best known Republican in Washington state, thanks to his two bids for governor. In an election that went into overtime, Rossi lost to Democrat Christine Gregoire by just a handful of votes six years ago. He was again defeated in a 2008 rematch by a wider margin.
Rossi's announcement came just days after Alaska Gov. Sarah Palin endorsed Didier, a Tea Party favorite, farmer and former professional football player with the NFL's Washington Redskins. Didier himself has attacked Rossi as a firmly entrenched member of the Republican establishment. The third GOP candidate polled in the survey, Akers, is a businessman.
Didier is expected to meet with staffers at the National Republican Senatorial Committee while in the nation's capitol this week. The NRSC played a role in encouraging Rossi to run this year for the Senate. While in Washington, Didier also met with Rep. Ron Paul of Texas, according to a tweet Wednesday afternoon by the candidate.
Polls of Washington state voters conducted earlier this year suggested that Rossi, a former state senator, could be competitive with Murray, the so-called Senate "soccer mom." But Murray is sitting on a formidable $6 million campaign war chest, according to disclosures filed with the Federal Elections Commission at the end of March, and handily won her reelection bids in 1998 and 2004.
The Elway Poll indicates that Murray leads Rossi 47 to 40 percent in a hypothetical November matchup, with Murray leading Didier and Akers each by 14 points in general election showdowns.
The Elway Poll was conducted June 9-13, with 405 registered voters in Washington state questioned by telephone. The survey's overall sampling error is plus or minus 4.9 percentage points.
Paul Steinhauser on Twitter: @psteinhausercnn