PHOENIX — Brushing aside her ties to the Clintons, Gov. Janet Napolitano on Friday endorsed the presidential candidacy of Illinois Sen. Barack Obama.

 And the reason? Freshness. “To me this election is fundamentally about change,’’ the governor said in announcing her endorsement at the senator’s Arizona campaign headquarters. “It’s about a new vision in Washington, D.C.,’’ she continued. “It’s about bringing people of different areas of the country together, people of different parties together, people of different ages together.’’

 Napolitano called Hillary Clinton “well qualified,’’ promising to campaign for her if she ends up the Democrat Party nominee. But the governor made it clear that she sees the senator from New York as a more representative of the politics of the past than those of the 21st century. “It was a decision about change,’’ Napolitano said. “It was a decision about freshness.’’

 Napolitano acknowledged she was named the U.S. Attorney for Arizona by Bill Clinton when he was elected president. As to Hillary Clinton, the governor said “we know and respect each other.’’

 But Napolitano said “choices have to be made.’’ Nor did the governor feel any obligation to support Clinton because she is the first woman who has a realistic chance of getting elected. Napolitano said she doesn’t view the campaign as being about gender or about race.

 Napolitano said one reason she decided to back Obama is because she believes he is the most capable candidate of handling th difficult issues facing the next president. These includ questions of immigration and border security, including revamping the nation’s visa policy to get the number of qualified workers needed and dealing with the estimated 12 million people already in this country illegally. “I’m confident that Sen. Obama is willing to take that very difficult issue up,’’ she said.

 The governor acknowledged that on the crucial issue of comprehensive immigration reform, the candidate whose view may come closest to hers is Arizona’s own John McCain. “But I think that Sen. Obama agrees with me in large part on immigration,’’ Napolitano said. “ And there are a lot of other issues in this race beyond immigration.’’

 Obama returned the compliments, telling reporters by phone that he — and any Democrat — would be wise to consider having the governor as a member of the Cabinet “She’s just a singular talent out there,’’ Obama said, saying Napolitano has dealt with difficult issues in “a common-sense way that brings people together,’’ saying she has “the kind of tone and temperament I’d want to see in my government.’’

 Napolitano brushed aside questions about whether she would take a Cabinet post — or possibly be a vice presidential candidate. “I am the governor of Arizona and intend to be the governor of Arizona,’’ she said.

 Kathleen Strand, a spokeswoman for the Clinton campaign, downplayed the importance of the endorsement, saying that the New York senator’s credentials are more important — and, by extension, suggesting Obama’s are insufficient. “We believe that, at the end of the day , e voters will make their decision on the qualifications, the plans and experience of the candidates and the person who is best ready to lead this country starting on Day One,’’ Strand said.

 Jim Haynes, president of the Behavior Research Center which does political polling, said it’s hard to gauge what the endorsement means in actually getting people to vote for Obama.If anything, Haynes said, the biggest impact is not going to be getting support for Obama but undermining the Clinton campaign.

 “They’re banking ... in really attracting women voters,’’ he said. “With Napolitano certainly being one of the most high-profile female officeholders at the state or local level in the country, it’s got to be a psychological approach at least to the Clinton campaign.’’