CLEVELAND -- As President Obama and his campaign rolled across Northern Ohio Thursday, and Mitt Romney had two high-profile Republicans trailing his every move, one political fact appeared to be clear.
Neither campaign thinks it can win the White House without winning Ohio.
"No Republican candidate has won the presidency without winning Ohio," says Dr. Joel Lieske, a political science professor at Cleveland State University, "so if Obama can carry Ohio, it's curtains for Romney."
But to win the state, Obama must run well in northern Ohio, particularly in Cleveland.
"Northern Ohio is the treasure trove of potential Democratic voters," says Dr. Justin Vaughn, also a political science professor at CSU, "so for a Democrat to win statewide, they've got to deliver as many potential Democratic votes as possible north of I-70."
Politically, in very simple terms, the state is divided by I-70, which cuts across the center of Ohio.
The northern half leans for Democrats, and the southern half -- especially southwest Ohio -- leans towards the GOP.
Republican Mitt Romney sent one former and one current GOP governor (Tim Pawlenty and Bobby Jindal) to shadow Obama's bus tour, criticizing the President's policies along the way.
Political observers say Romney knows that if he is to win Ohio, he can lose Cleveland and Cuyahoga County badly ... just not too badly.
Indeed, President Obama trounced Sen. John McCain in the 2008 race in Cuyahoga County, when McCain got under 200,000 votes in the county.
Obama won Ohio and the presidency.
But, in 2004, President George Bush won about 221,000 votes in the county.
He won Ohio and the presidency.
The last time a Democrat won the presidency without winning Ohio was John Kennedy back in 1960.