GRESHAM, Ore. (AP) — Trying to help Monica Wehby rescue her campaign for the U.S. Senate, Arizona Sen. John McCain said Thursday that the Oregon doctor would be a strong advocate for veterans and a much-needed expert on health care.

McCain told an audience comprised largely of veterans that Wehby knows how to fix problems plaguing the Veterans Administration health care system. While training for her medical career, Wehby said she did work at a VA hospital in Los Angeles.

"This will be the instant expert," McCain told an audience comprised largely of veterans at a Veterans of Foreign Wars hall in Gresham, outside Portland. "This will be the go-to person in the United States Senate when we're talking about all the things that need to be done for our veterans."

The Arizona Republican trained most of his fire on President Barack Obama, who defeated McCain for the presidency in 2008. But he offered a sharp critique of Democratic incumbent Jeff Merkley's work to change the Senate's obscure filibuster rules.

"It's the worst single act that I have seen in my years in the United States Senate, and Sen. Merkley led it," McCain said in an interview with The Associated Press.

Merkley says the filibuster rules, which allow a minority of 41 senators to block legislation, supports gridlock that paralyzes Congress. Since he joined the Senate, he has led the charge to change the rules and finally achieved a partial victory late last year. McCain said Merkley deprived the minority party of its "constitutional obligation" to review nominations submitted by the president.

Pitching herself in a state dominated by Democrats, Wehby says she's an independent thinker who won't be beholden to the Republican Party. McCain's backing gives her the approval of a senator known best for his willingness to buck his party on high-profile issues.

"I think our maverick here is similar to the way I would act," Wehby told the AP, seated next to McCain on a couch at a Salem hotel and conference center where the pair were set to raise money for Wehby's campaign.

McCain downplayed the maverick label and tacked to the right under pressure from a tea party challenger during his 2010 re-election campaign, but he's more recently stood up to the no-compromise wing of his party.

In a statement, Merkley's campaign said the support of the Republican Party's former presidential candidate shows Wehby is "a typical Republican who would rubber stamp the agenda of Senate Republicans."

Wehby's campaign has been beleaguered by a series of stories from her campaign and personal life, including old police reports showing an ex-husband and former boyfriend had both made harassment complaints against her. She also was accused of plagiarizing her health care and economic plans, and has been slammed by news organizations for skipping debates and endorsement interviews.

McCain insisted Wehby was in "a winnable race" and urged the crowd in Gresham to work hard to help her get elected. Acknowledging that he had "a selfish reason" for helping Wehby, he said her race could prove pivotal in determining which party controls the Senate."