GOP presidential candidate Rick Santorum will bring his campaign to Olympia and Tacoma on Monday.

Washington will become a flash point in the nation’s culture wars on Monday, as Republican presidential contender Rick Santorum brings his socially conservative message to the state on the same day Gov. Chris Gregoire is expected to sign a bill legalizing gay marriage.

In his first foray here in advance of the state’s March 3 GOP caucuses, Santorum is planning a 7 p.m. campaign rally Monday at the Washington State History Museum in Tacoma, according to plans sent by his campaign to state Republican leaders.

Before that, Santorum will meet at an Olympia church with a group of “values voters” opposed to gay marriage. Santorum is also expected to meet with the state House and Senate Republican caucuses, said Kirby Wilbur, state GOP chairman.

It is the first scheduled visit from one of the Republican presidential contenders ahead of the GOP caucuses, which will be a prize this year with the party’s nomination battle nowhere near settled.

Santorum, the former Pennsylvania senator, has been riding a recent tide of popularity among Republican voters looking for an alternative to former Massachusetts Gov. Mitt Romney.

He swept Republican contests this week in Colorado, Minnesota and Missouri, and a Fox News poll showed him tied with Romney nationally among GOP primary voters.

Santorum’s Washington visit will coincide with Gregoire’s planned signing of the bill approved by the Legislature that would make Washington the seventh state to legalize same-sex marriage.

A darling among social conservatives — and a villain to gay-rights supporters — Santorum has said that gay marriage undermines society and families. In 2003, he said a Supreme Court decision legalizing homosexual sex could create a precedent allowing bigamy, polygamy and incest.

The Santorum campaign did not respond to requests for comment on the timing of his visit.

Up to now, Santorum’s campaign had lagged in organizing here behind Romney, who has lined up establishment endorsements and donors, and Texas Congressman Ron Paul, who has a core of dedicated volunteers working to turn out supporters to the caucuses.

While Santorum has no paid staff here yet, he has in the past week or so organized a volunteer presence that is rapidly gaining support, said Graden Neal, an Ellensburg Republican activist who is volunteering as co-state leader for the campaign.

“To me, Rick Santorum is clearly the best candidate left,” Neal said.

“He doesn’t have the excess baggage that [former House Speaker] Newt Gingrich has, and he doesn’t have the flip-flopping problem that Mitt Romney has,” Neal said, adding that Paul is too weak on defense.

Washington’s Republican caucuses will matter more than they have in years, state GOP officials have predicted.

The caucuses will land this year just before Super Tuesday, when 10 states hold nominating contests.

Technically, the state’s 43 delegates won’t be awarded to any candidate on March 3 — they will not be bound to a candidate until the GOP state convention in June.

Still, the results of the caucus straw poll are expected to draw national attention and give momentum to the winner headed into Super Tuesday.

Romney is planning a fundraising trip to Washington on March 1. The Gingrich and Paul campaigns have not announced plans.

Meanwhile, President Obama is scheduled to attend two fundraisers and an official event in Seattle Friday.

Jim Brunner: 206-515-5628 or jbrunner@seattletimes.com.

On Twitter @Jim_Brunner.