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.