OLYMPIA, Wash. -- The Seattle Times Co. began an active campaign Wednesday to support Republican gubernatorial candidate Rob McKenna and gay marriage, part of a push to demonstrate the effectiveness of newspaper political advertising.

Washington state's largest newspaper began with a full-page ad calling McKenna "a choice that will make us all proud." The newspaper's editorial board has endorsed McKenna over Democratic candidate Jay Inslee in what is one of the most watched campaigns for governor in the country.

The company said it's also giving an in-kind donation of ad space to the political campaign that supports the gay marriage ballot measure that will be decided by state voters next month. In a statement, the company said it hopes the advertising effort will demonstrate the strength of print political advertising, noting that political ad spending mostly focuses on broadcast and direct mail.

"This is a business decision that is completely separate from journalism functions of the newspaper," said Alan Fisco, executive vice president for revenue and new products at the newspaper, in a statement. "The ads will be clearly identified as ads and there is no intersection between the advertising and our editorial commentary or news reporting."

Times spokeswoman Jill Mackie said the contributions to the two campaigns would be valued at about $75,000 each. She said that value means ads will appear a number of times in various forms between now and Election Day.

Inslee's campaign said the ads raise serious questions about objectivity.

"Copy for the ad had to be written, artwork had to be prepared by someone," said Inslee spokesman Sterling Clifford. "It is difficult to believe that none of the Times' supposedly neutral newsroom resources were used for this partisan ad."

Roy Peter Clark, who teaches writing and ethics at the Poynter Institute, said the advertising poses challenges for the newspaper and its credibility. He said readers already have the misconception that editorials supporting a candidate indicate bias in the paper's reporting, even though outlets typically work to separate their news and opinion operations.

"It seems like what they're trying to do now builds another kind of a credibility obstacle for the people who are doing the reporting on the ground," Clark said.

Clark said the problem isn't a new one as various newspaper companies over the years have waded into political or policy issues.

The newspaper's ad that was published Wednesday will have to be reported as an independent expenditure within 24 hours, according to the Public Disclosure Commission.