WASHINGTON (CNN) -- With just days to go before Election Day, Sen. Barack Obama is warning his supporters that things are going to get unpleasant fast -- and that the race will come down to every last vote.
"Don't believe for a second this election is over. Don't think for a minute that power concedes anything. It's gonna get nasty, I'm sure, in the next four days," Obama told a crowd in Columbia, Missouri, on Thursday night.
"They will throw everything at us like they've been doing, and we're gonna have to work like our future depends on it in this last week. You know what? Because it does, and every single young person here tonight -- I've gotta have every single one of you voting, and you've gotta grab five more, all of you, have gotta vote," he said.
The warning comes after the Illinois senator said in an interview Thursday night that his campaign was winning -- some of the most confident language from Obama since he won the Democratic nomination.
"I think we're winning right now," he told MSNBC's Rachel Maddow. "Maybe I'm doing something right."
And that confidence from Obama may be expanding, despite assurances that the race is going to narrow. Watch more on the state of the race »
On Friday, Obama campaign manager David Plouffe told reporters in a conference call that the campaign is encouraged by results of massive get-out-the-vote efforts in early voting states.
Plouffe said the campaign is pleased that a large part of the early vote so far is coming from sporadic and new voters
"The die is being cast even as we speak," he said. Watch more on a possible early voting earthquake »
Early voting in Colorado, Nevada and Texas ends Friday. North Carolina's early voting ends Saturday, and Florida's ends Sunday. Early voting in Ohio and Indiana -- states where polls show a neck-and-neck race -- ends Monday.
The Obama campaign is also looking to expand its electoral map strategy. On Friday, the campaign announced that it was going on the air in Sen. John McCain's home state of Arizona for the first time this cycle.
The news comes as a new CNN poll of polls, released Friday morning, finds the Republican nominee leading Obama there by just 4 percentage points, 49 to 45 percent. Six percent of the state's voters said they were unsure about their presidential pick. Watch more on Obama's efforts in GOP-leaning states »
Plouffe told reporters that the Obama campaign's positive spot, "Something," will hit the airwaves in Arizona. He also said the campaign was going back on the airwaves in Georgia and North Dakota with its negative spot, "Rearview Mirror," which ties McCain to President Bush.
Obama plans to campaign this weekend in Colorado, Nevada and Missouri. His running mate, Sen. Joe Biden, plans rallies in Indiana and Ohio.
Earlier this week, the McCain campaign and the Republican National Committee launched negative robo-calls in Arizona telling voters that Obama was unready to handle an international crisis.
On Thursday, MoveOn.org announced that it was targeting McCain with ad buys in each of the state's major media markets. The Obama campaign also issued a call for volunteers there, citing tightening polls in the state.
McCain spokesman Tucker Bounds dismissed the new Obama push Friday morning, calling it a "waste of his resources."
McCain, meanwhile, continues to hammer his opponent for exuding confidence in the final days of the campaign. He has been repeating a standard campaign line recently, saying Obama is "measuring the drapes" for the White House.
At a campaign rally Friday morning, McCain expressed confidence that the tide was turning in his favor.
"I want to tell you the enthusiasm and the momentum that I feel here in Ohio is going to carry us to victory here in Ohio and throughout this country," McCain told supporters in Hanoverton, Ohio. Watch McCain fight for the battleground state of Ohio »
A CNN poll of polls in Ohio calculated Wednesday indicates that Obama has an 8-point lead in the state, with the Illinois senator ahead of McCain 50 percent to 42 percent, with 8 percent unsure.
No Republican has ever won the presidency without winning Ohio.
And the Republican ticket is wasting no time in reaching out to other battleground state voters.
Vice presidential candidate Sarah Palin plans on holding five rallies Saturday in Florida, North Carolina and Virginia -- states where the two campaigns are locked in a close race.
On Sunday the Alaska governor will campaign in Ohio, then travel to Iowa.
McCain will hold rallies this weekend in Virginia and Pennsylvania -- both states where Obama is leading, according to several recent polls.
And just two weeks after his running mate made an appearance on NBC's "Saturday Night Live," a McCain campaign aide tells CNN that the Republican presidential nominee will appear on the the late-night comedy show Saturday.
McCain has appeared on the show several times over the years.
His most memorable appearance on the long-running show was in October 2002, when he hosted the program for a night. In a spoof commercial hawking an album called "McCain Sings Streisand," he sang several of Democratic loyalist Barbra Streisand's songs.
CNN's Candy Crowley, Dana Bash, Rebecca Sinderbrand and Thom Patterson contributed to this report.