"I will compete very strongly here in the heartland of America," the Republican nominee-in-waiting said in Ohio, underscoring the importance of the state and the region as he embarks on an eight-month effort to cobble together the 270 electoral votes needed to win the White House.
It was fitting, then, that McCain chose this setting - a state that gave President Bush the 2004 election in a swing-voting region
- to step up his rhetoric against the man he considers his most likely opponent this fall.
"I will fight every moment of every day in this campaign to make sure Americans are not deceived by an eloquent but empty call for change," McCain said after winning the Wisconsin primary. It was a thinly veiled suggestion that the Illinois Democrat, who has now won 11 straight primary and caucus contests over Hillary Rodham Clinton, lacks the experience, judgment and character a president needs.
Well into the week, however, a character controversy of his own overshadowed McCain's message.
At a news conference in Toledo on Thursday, McCain was forced to respond to published reports that alleged he showed favoritism to clients of a female telecommunications lobbyist. A New York Times report said top McCain aides became "convinced the relationship had become romantic."
With his wife, Cindy, beside him, he denied any romance or impropriety.
"It's not true," McCain said. "At no time have I ever done anything that would betray the public trust."
"We will move forward," he declared and continued his Midwest trek.
With Obama and Clinton still fighting for the Democratic nomination, the GOP's likely standard-bearer is laying groundwork now for the fall by visiting key states and trying to define his opponents, particularly Obama.
Thus, McCain took his sharper criticism of Obama to five middle America states this week.
He began in Wisconsin, at a county GOP dinner and a get-out-the-vote rally. By Tuesday, he was in Ohio celebrating a Wisconsin victory that inched him closer to the 1,191 convention delegates he needs to clinch the nomination.
McCain also stopped in Illinois on Wednesday and toured a Ford Motor Co. assembly plant in Michigan on Thursday. He rounds out the week Friday in Indiana with a town-hall style meeting.
The Arizona senator was also raising cash in each state. He kept a busy fundraising schedule for someone who doesn't like the chore. "We've got a lot of work to do," McCain acknowledged.
His attention to this region is no surprise.
The Midwest has been hotly contested in recent presidential elections. Both Republicans and Democrats plan to focus on it again this fall.