Barack Obama's presidential campaign plans to extend its advertising expenditures in the last five days until the election, including a buy in Arizona.

The decision to go on the air in John McCain's home state follows several recent polls showing the GOP candidate's lead slipping there.

McCain might be losing confidence in his chances in his home state, too. The GOP candidate plans to campaign in Prescott, Ariz., on Monday, the day before Election Day.

Obama campaign manager David Plouffe said Friday the campaign also would resume advertising in Georgia and North Dakota, two states that solidly backed President Bush four years ago and now seem that they could be in play.

Earlier in the year, Obama established robust organizations in North Dakota and Georgia, but his campaign scaled down its operations to focus on more competitive states like Virginia and Colorado, which are trending towards Obama.

Plouffe said the campaign maintained staff and volunteer organizations in Georgia and North Dakota and is more optimistic about its chances based on promising signs from early voting in Georgia. Polls show Obama and McCain are essentially tied in both North Dakota and Georgia.

Arizona, one state no one thought could be in play just a month ago, is proving not to be the lock McCain hoped it would be. The Republican candidate felt compelled to run automated phone calls to voters in his home state this week.

"If someone else had been the Republican nominee, I think Arizona would be a core battleground, like it's western neighbors," Plouffe said.

McCain's home state advantage seems to be slipping, he added, and the campaign's "internal data would suggest that this could be a very close race." is running its own ad targeting Republicans for Obama in Arizona as well.

In Arizona, the Obama campaign will be airing what it calls its "positive" closing argument ad, which touts Obama's endorsements from Warren Buffet and Colin Powell.

In North Dakota and Georgia, Plouffe said, the campaign will be running a more negative spot that links McCain to President Bush's economic policies.