Washington’s Senate race looks increasingly like a referendum on incumbent Democrat Patty Murray with two Republican candidates edging past her this month.

A new Rasmussen Reports telephone survey of Likely Voters in Washington State finds Republican hopefuls Dino Rossi and Clint Didier both earning 48% support in match-ups with Murray. She, in turn, picks up 45% of the vote against the two GOP challengers. Less than 10% of voters in both cases prefer some other candidate in the race or are undecided.

In June, Murray and Rossi were tied as they have been in virtually every survey this year. Since the beginning of the year, Murray has earned 46% to 48% of the vote, while Rossi’s support has ranged from 46% to 49%.

Incumbents that fall short of 50% at this stage of a campaign are considered potentially vulnerable, but worrisome for Murray is that this is her poorest showing of the year. She was reelected to a third term in 2004 with 55% of the vote.

Washington is one of nine states currently characterized as Toss-Ups in the Rasmussen Reports Senate Balance of Power rankings.

Last month, Murray led Didier, a former professional football player, 48% to 40%. Prior to that survey, Didier’s support had ranged from 30% to 37% since January. In the same time period, Murray earned 47% to 51% in match-ups with Didier.

A third Republican hopeful, businessman Paul Akers, continues to trail Murray. But in the latest survey, the incumbent leads Akers 46% to 41%, while a month ago she was ahead 48% to 38%.

Republicans will pick their candidate in an August 17 primary, but Rossi, a two-time unsuccessful candidate for governor, is still considered the favorite in the race.

(Want a free daily e-mail update? If it’s in the news, it’s in our polls). Rasmussen Reports updates are also available on Twitter or Facebook.

The survey of 750 Likely Voters in Washington was conducted on July 14, 2010 by Rasmussen Reports. The margin of sampling error is +/- 4 percentage points with a 95% level of confidence. Field work for all Rasmussen Reports surveys is conducted by Pulse Opinion Research, LLC. See methodology.

Male voters prefer the Republican in every matchup, while female voters lean toward the Democrat.

Among voters not affiliated with either major party, Rossi leads by slightly better than two-to-one. Didier fares nearly as well, with Akers ahead but not as strongly in this group.

Just seven percent (7%) of Washington voters now rate the economy as good or excellent, while nearly half (49%) say it’s poor. Thirty percent (30%) think the economy is getting better, but 45% say it’s getting worse.

Seventy-two percent (72%) say the country is in recession.

Support for last year’s $787-billion economic stimulus plan which Murray supported is higher in Washington than it is nationally with voters in the state closely divided over whether it helped or hurt the economy. But even in Washington, only 30% think the increased spending in the stimulus plan created new jobs, while 52% disagree and say it did not create any new jobs.

By a 58% to 25% margin, voters in the state say cutting taxes is a better way to create jobs than increasing government spending.

Fifty-four percent (54%) of Washington voters favor repeal of the national health care bill, which Murray supported, while 44% oppose repeal. This is in line with voter sentiments nationally and includes 43% who Strongly Favor repeal and 37% who are Strongly Opposed.

Murray earns nearly 90% support in all three matchups from those who Strongly Oppose repeal. Rossi and Didier run nearly as strongly among those who Strongly Favor repeal.

Thirty-seven percent (37%) of all voters in the state agree with the U.S. Justice Department decision to challenge Arizona’s new immigration law in federal court. Fifty-six percent (56%) disagree with this decision, identical to opposition nationally.

But support for a law like Arizona’s in the state is lower than support nationwide. Fifty-three percent (53%) of Washington voters favor passage of such a law in their state, but 38% are opposed.

Murray is viewed Very Favorably by 28% of voters in the state and Very Unfavorably by 36%, up five points from a month ago.

For Rossi, Very Favorables are 27% and Very Unfavorables 20%, down five points from the previous survey.

Fourteen percent (14%) have a Very Favorable opinion of Didier, while 16% view him Very Unfavorably.

Just five percent (5%) share a Very Favorable view of Akers, with 12% who regard him Very Unfavorably. But like Didier, a sizable number of voters in the state don’t know enough about him to venture any kind of opinion. Rossi and Murray are very well-known, by comparison.

At this point in a campaign, Rasmussen Reports considers the number of people with strong opinions more significant than the total favorable/unfavorable numbers.

Marking little change from last month, 50% of the state’s voters approve of the job President Obama is doing, while 49% disapprove. This is slightly better than Obama’s job approval ratings nationally in the Rasmussen Reports daily Presidential Tracking Poll.

Forty-two percent (42%) approve of Democratic Governor Christine Gregoire’s job performance, but 55% disapprove. This, too, is virtually unchanged from the previous survey.