Republican Mitt Romney's lead over President Barack Obama in Arizona has shrunk to 3 percentage points in a new poll that has renewed speculation that the traditionally GOP-leaning state could swing toward the Democrats this year.

The mostly automated telephone survey of 600 likely Arizona voters, conducted Sept. 15 to Wednesday by the bipartisan consulting firm Purple Strategies, indicated that Romney was ahead of Obama 48 percent to 45 percent, with 7 percent still not sure.

That's well within the poll's margin of error of plus or minus 4 percentage points. About 25 percent of the survey's interviews were conducted online with people who rely on mobile phones.

John McCain, the senator from Arizona who topped the GOP ticket in 2008, carried his home state four years ago, but earlier this year it appeared that Obama was poised to put the state in play.

However, subsequent Arizona polls showed Romney with a clear advantage. A Sept. 9 poll by Public Policy Polling, a Democratic firm based in North Carolina, showed Romney with a lead of 9 percentage points. Prior to the Purple Strategies poll, Nate Silver, the New York Times' political polling expert, was forecasting a 92.1 percent chance of a Romney win in Arizona.

A Democrat has not carried Arizona since President Bill Clinton did so in 1996, a year in which third-party candidate Ross Perot also was on the ballot. Clinton's re-election win was the first Democratic victory in Arizona since President Harry Truman won the state in 1948.

Doug Usher, Purple Strategies managing partner and pollster, said recent controversies surrounding Romney's criticism of the White House response to the attack on the U.S. Consulate in Libya and negative comments about the "47 percent" of Americans who support Obama could have cost the Republican nominee several percentage points in Arizona and other states.

He said the tighter Arizona results likely reflect national changes in a race that he said appears to be moving in Obama's favor.

Larry Sabato, director of the Center for Politics at the University of Virginia, said he wasn't putting much stock in the Purple Strategies poll, emphasizing that Obama likely would have to win re-election in "a complete blowout" to carry Arizona.

"It would be the surprise of Election Night, and it would signal that it's a massive landslide," Sabato said. "While the Obama people no doubt hope for that, the odds are against it."

Another national political analyst said he was "cautiously skeptical" of the poll showing a close Arizona race.

"I haven't heard a lot of buzz from Democrats that the state is in play," said Stuart Rothenberg, publisher and editor of the nonpartisan Washington-based Rothenberg Political Report. "That doesn't mean Tuesday morning I won't start hearing it, but I haven't heard it yet."

Nowicki is The Republic's national political reporter. Follow his blog at azdc.azcentral.com.