Democrat Barack Obama returned Friday morning to Iowa, where his victory in the presidential caucuses gave his drive for the White House a major boost, while Republican John McCain headed into the final weekend of the election season with a call to supporters to prove the polls wrong.

Three days before Election Day, McCain was in Ohio, a must-win Republican state. "We're a few points down, but we're coming back and we're coming back strong," he said at a rally Friday morning. "We're closing, my friends, and we're gonna win in Ohio."

McCain plans a marathon of visits to as many as eight states on Monday. His campaign also announced Friday that the senator from Arizona would attempt to show voters his funny side with an appearance this weekend on "Saturday Night Live."

Ohio, which is worth 20 of the 270 electoral votes needed to win the presidency, is a symbol of just how far McCain has to go with just days left. Polls show that he is trailing in the national popular vote, and Obama is ahead in some states, such as Ohio, that the GOP won in 2004. McCain finds himself in the unenviable position of defending Republican states while attacking in just one Democratic state, Pennsylvania, where his vice presidential running mate, Sarah Palin, campaigned Friday.

McCain continued to criticize Obama's tax policies -- which the Republican campaign has said are too liberal, even socialist, because they would redistribute wealth by raising taxes on the rich. Obama defends the plan, saying it is fair to have those earning more than $250,000 a year pay more in taxes.

The Democratic candidate made those same points to about 25,000 supporters sprawled across a downtown plaza in Des Moines on Friday. He stressed the reform themes that were central to his successful yearlong campaign to win the Iowa caucuses Jan. 3.

The senator from Illinois said he admired a presidential candidate who said in 2000, "I will not take the low road to the highest office in this land." Then Obama added: "Those words were spoken eight years ago by my opponent, John McCain. But the high road didn't lead him to the White House then, so this time, he decided to take a different route."

Calling on Iowans to "beat back this kind of politics" once and for all, Obama said, "We have the chance to prove that the one thing more powerful than the politics of 'anything goes,' the one thing the cynics didn't count on, is the will of the American people."

In white shirt sleeves at a lectern decorated with hay bales and pumpkins, Obama told the crowd, "You helped launch this campaign. So, the people of Iowa, I will always be grateful to all of you."

Obama's outdoor rally on an improbably warm, sunny Halloween in Des Moines was part of his final sprint across states that President Bush won in 2004. In the days left before Tuesday's election, Obama plans to campaign in Indiana, Nevada, Colorado, Missouri, Ohio, Florida, North Carolina and Virginia.

The Obama campaign, flush with resources, continued to expand its reach across the political map, announcing plans to launch TV ads in Georgia, North Dakota and McCain's home state, Arizona.