SEATTLE — President Barack Obama rallied an arena full of supporters Thursday at the University of Washington alongside Sen. Patty Murray, whose seat could decide control of the Senate.

When the Washington state Democrat first ran in 1992, Obama said, “She was the mom in tennis shoes who just wanted to help a few people and solve a few problems. All these years later, that’s exactly what she’s done. … Now she needs our help so she can keep fighting in the United States Senate.”

Murray faces Republican Dino Rossi, who mentioned his distinction as the potential 10th and deciding Republican pickup in two stump speeches he delivered Wednesday in Yakima and Olympia.

Obama made note of another Rossi feature that sets him apart.

“Patty Murray’s opponent has the distinction of being the first candidate in the country to call for the repeal of Wall Street reform,” Obama said. “Folks, it is up to you to say we are not buying what you are selling.”

Murray and Obama walked on stage together to a roaring ovation from the crowd. After embracing, Murray spoke. She focused on her work on behalf of veterans, but also took a few shots at Rossi.

“My opponent is running on what he wants to take away from you. My opponent has spent his entire campaign on one word: ‘No,'” Murray said. “I think we deserve better than a one-word answer to every problem. We deserve better than Di-NO.”

Obama is the third Democratic heavy hitter to stump in Washington for Murray this week. President Bill Clinton was in Everett on Monday, and on Tuesday vice president Joseph Biden was in Vancouver, in the southwestern part of the state, on Tuesday.

“Sen. Murray is bringing in her D.C. friends because clearly they’re terrified about what Nov. 2 is going to bring,” Rossi said Wednesday in an interview from his Olympia call center. “But 18 years of taxing and spending and growing government is something that people are going to reject in the state of Washington.”

The commercial real estate broker and former state Senator is running his third statewide campaign in six years, after losing to Democratic Gov. Christine Gregoire in 2004 and 2008.

Obama’s visit came as polls showed the race within the margin of error and a week after ballots were mailed to voters. All but one of Washington’s 39 counties vote primarily by mail. Ballots must be postmarked by Election Day.

“If you haven’t already voted for Patty Murray, let me be clear — you need to go right after this rally, fill out that ballot and mail it in,” Obama said. “Not tomorrow, not the next day, but today.”

Nearly two years since being elected president, Obama still receives a rock star welcome from supporters. Many of the 10,000 attendees in Hec Edmundson Pavilion were students, and along with a mix of older voters, they cheered loudly throughout the event.

As they waited for the program to begin, a few students standing near the press ring said they had not been following the race closely and attended the rally mostly to see Obama, but they would definitely be voting for Murray.

A couple of older voters said they were there to see Obama as well, and remarked about the negative ads from both parties that have flooded the airwaves.

Along with Murray and Rossi ads, outside groups are on radio and TV airwaves. A radio ad from the National Education Association accusing Rossi of not supporting the troops aired multiple times Wednesday.

And a National Republican Senatorial Committee ad against Murray aired in Seattle during the Wednesday night Fox broadcast of the Major League Baseball playoffs.

Speaking before Obama and Murray were 8th district Democratic nominee Suzan DelBene, who is challenging Republican Rep. Dave Reichert, and Democratic Reps. Jay Inslee and Norm Dicks.

Rep. Jim McDermott was in attendance as well, but did not speak. He stood near the press as Obama was speaking and took a picture on his iPhone.

Dicks, who is in line to chair the Appropriations Committee if Democrats retain control of the House, urged the crowd to help Democrats pull off a Truman-like comeback to keep the party in the majority.

Before closing his speech, Obama again urged rally attendees to get involved in the election.

“If everybody who voted in 2008 shows up in 2010,” he said, “we will win this election.”

Before reaching the rally, Obama stopped at a local donut shop, Top Pot Doughnuts in the Belltown neighborhood. He then spoke and took questions about women and the economy to about 30 people in the backyard of Erik and Cynnie Foss’s Seattle home.

Later, at the rally, Murray noted that Washington was the only state with a female governor and two women Senators.

“It think it’s fair to say Washington state women win,” she said.