Rep. Mark Olson's tumultuous relationship with the state Republican Party has gone sour again.

The Big Lake legislator, recently given a surprising endorsement by local Republicans for a special election in a state Senate district, is being rejected by fellow Republicans in the Senate, who say he will not be welcome in their caucus because of a domestic assault conviction that had earlier inspired the House GOP caucus to expel him.

On Thursday, U.S. Sen. Norm Coleman weighed in, saying he thinks the party should distance itself from Olson.

Olson's endorsement last week for a seat being vacated by Sen. Betsy Wergin, R-Princeton, initially appeared to catch Republican Senate leadership flatfooted. On Thursday, the leaders responded with a statement announcing their support for Olson's primary opponent.

"While we respect our endorsing process in the Republican Party, some things rise far above process and party in terms of importance. The integrity and character of our candidates and elected officials are two of those things," the statement said.

The statement, penned by Senate Minority Leader Dave Senjem, R-Rochester, and five assistant minority leaders, strongly endorsed Olson's GOP primary opponent, Alison Krueger.

Krueger, the statement said, "combines excellent conservative credentials with a high degree of personal integrity and character," and that the Senate GOP caucus is encouraging Republicans to vote for her in the Sept. 9 primary. She had agreed to abide by the party's endorsement and is not actively campaigning.

Coleman's statement opposing Olson also was unusual in its candor for a sitting U.S. senator, saying the party's endorsement of Olson is "simply unacceptable and unsupportable." Coleman also urged party officials not to provide any support for Olson's campaign should he emerge victorious from the primary, even if it risks losing a Senate seat.

"We must maintain and uphold our beliefs that violence of any kind, whether it is in word or in deed, should not be rewarded with our party's support," Coleman said.

The latest moves come in apparent response to a denunciation of Olson's endorsement by a blogger who usually reserves his fire for Democrats. Michael Brodkorb, author of Minnesota Democrats Exposed, launched a fusillade against GOP leaders for failing to repudiate Olson's endorsement.

"It is an embarrassing and sad fact, but if Representative Olson wins in November he will become a more influential member of the Minnesota Legislature because he was arrested, charged, tried and convicted of domestic assault," Brodkorb complained.

Olson did not return calls for comment. A spokeswoman for the Minnesota Republican Party said state GOP supports "local control" over its endorsement process.

Olson was convicted last year by a Sherburne County jury of misdemeanor domestic assault for causing his wife fear of bodily harm when they collided and fell to the ground behind their home in November. He was acquitted of intentionally harming or trying to harm her after his attorney argued that he had acted in self-defense in an abusive relationship.

Shunned by the House GOP caucus after his conviction, the eight-term House member decided in July not to file to run for reelection, saying that he was concerned about being a career politician. But less than a month later, he sought and received the Senate district endorsement to replace Wergin, who is stepping down after being named by Gov. Tim Pawlenty to the state's Public Utilities Commission.

Olson gained the endorsement for the District 16 Senate seat on the second ballot against Kruger, of Big Lake. Her name will remain on the ballot for the Sept. 9 primary.

DFLer Lisa Fobbe also has filed to run in the special election, which will be held on the same date as the general election, Nov. 4.

Mark Brunswick • 651-222-1636