Nowhere is the pressure to win being felt by McCain staffers and surrogates quite the way it is in Ohio.
No Republican has ever won the presidency without winning Ohio, and the state is key to virtually any chance McCain has for victory.
"Whoever wins Ohio is president of the United States," said Marty Judd, a Fairfield, Ohio, city councilman and regional vice-chair of the Butler County Republican Party.
"I think it was a very good strategic move," said Judd of McCain's decision to leave Michigan. "Michigan is generally a blue state. The McCain campaign has to concentrate on the big three: Ohio, Virginia and Florida. If we win those three states, then John McCain and Sarah Palin will be sworn in."
McCain's chances of victory in Michigan aside, some observers believe the McCain campaign's finances may also have played a role in the Republican's decision to abandon the race there.
The Republican presidential nominee, unlike Obama, is restricted in his fundraising options because he took federal funds. While Obama can raise funds by simply e-mailing his supporters and asking for donations, McCain must conduct traditional fundraisers, which waste time and resources that could be better spent in battleground states.
"We're seeing the impact of Obama's decision not to take public funding," said former McCain adviser Dan Schnur. "McCain has a finite number of resources and has to make triage-level decisions that most campaigns have had to make in the past. Deciding to bow out of a state -- like Michigan and perhaps he'll have to abandon Pennsylvania -- is standard for a campaign under those restraints. Obama is fortunate enough to not have to worry about it. It gives him much more leeway."
Opinion polls have Obama leading every battleground state -- Colorado, Florida, Michigan, New Hampshire, New Mexico, Nevada, Ohio, Pennsylvania, Virginia and Wisconsin. He is also leading in two states carried by George Bush in 2004, Iowa and New Mexico. If he wins all of those states on Election Day, he is just six electoral votes away from the 270 he needs to win.