A new poll concludes that Arizonans believe Sen. Barack Obama poses the biggest challenge to John McCain in the presidential race, but that the Arizona senator will ultimately win the White House.

The poll of 577 registered voters found that voters favored McCain over Obama 47 percent to 38 percent. They favored McCain over Sen. Hillary Rodham Clinton 53 percent to 37 percent.

The voters polled said they believe McCain likely will beat Obama in November. A similar February poll showed Arizonans thought Obama would beat McCain.

The poll was conducted April 24-27 by the Walter Cronkite School of Journalism and Mass Communications at Arizona State University and Channel Eight/KAET-TV. The survey has a sampling error of plus or minus 4 percentage points.