CHICAGO (CBS) – The critical midterm elections are just hours away. One thing you’ll be asked to decide is: who will fill President Barack Obama’s old Senate seat?

And one day out, the race is a toss-up between Republican Mark Kirk and Democrat Alexi Giannoulias. CBS 2’s Dana Kozlov reports on a day of going the distance for both candidates.

More than 600 miles each. That’s how many frequent flier miles both candidates racked up on their last, big day of campaigning Monday.

One respected political website calls the Kirk/Giannoulias battle the most-watched Senate race in the country. That’s one reason both candidates are spending the day trying to reach as many voters as possible.

It started at the crack of down for Republican Mark Kirk, who began shaking hands in Chicago. Kirk then flew to Springfield, then to Champaign. He was in Cahokia near St. Louis in the late afternoon and scheduled to arrive in Wheaton for an evening rally.

Kirk calls it a touch campaign but believes voters will cast their ballot based on each candidate’s economic vision.

That’s if they vote. Getting people to the polls is one of Congressman Kirk’s main goals.

Voter turnout will be critical in this race. But Kirk is taking the glass half-full approach, and says he believes a lot of independent voters are breaking down and leaning Republican, and points out he’s leading in the polls.

That depends, of course, on what poll you’re looking at. Kirk’s campaign is citing one that puts him ahead by four points.

Alexi Giannoulias’ campaign says another poll puts the state treasurer ahead by two points. Both, though, are really statistical dead heats. Again, another reason for the massive, statewide campaign push.

For his part, Giannoulias flew right to downstate Marion, then Springfield, Peoria and ended the afternoon in Chicago shaking hands at the “L” stop on Fullerton.

Giannoulias says he’s the candidate who will bring fresh ideas and a fresh perspective to Washington.

The downstate push isn’t a surprise.

Kirks wants to make sure he hangs on to the predominantly Republican voters downstate while Giannoulias is trying to win over as many votes as he can.

But this race in unpredictable at best.

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