UPDATED 11/2/10 6:38 a.m.

CHICAGO (CBS) – Illinoisans could be up late Tuesday night watching the results of the race to open the U.S. Senate seat once held by President Barack Obama.

Within an hour of the opening of the polls Tuesday morning, the race between Republican Mark Kirk and Democrat Alexi Giannoulias was too close to call.

Both candidates have been crisscrossing the state looking for any edge they can get.

On Tuesday, Kirk spent the day shaking hands from Chicago to Springfield, while Giannoulias hop-scotched to Springfield and Peoria.

CBS 2’s Dana Kozlov reported Monday that both candidates racked up more than 600 miles in the Illinois skies.

One respected political website calls the Kirk/Giannoulias battle the most-watched Senate race in the country, given that it’s for the seat once held by the president. That is one reason both candidates are spending the day trying to reach as many voters as possible.

Voter turnout will be critical in this race. But for Kirk’s part, he’s been 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.

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.

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

Overall, CBS News Chief Washington correspondent Bob Schieffer says to some degree, the die is cast for major Republican victories across the country Tuesday night.

LISTEN: Newradio 780 Political Editor Craig Dellimore Reports

Schieffer tells Newsradio 780 the situation doesn’t look as bleak for Democrats as they did six weeks ago. But Democrats are still in trouble.

Schieffer says the indications are the Republicans will win control of the House, but fall short of taking the Senate.

He adds that even if the Republicans make big gains on Capitol Hill, they will not have clear sailing, given that voters give low approval ratings to members of Congress no matter what the party.

Schieffer says this should be an incentive for bipartisanship.

Both Giannoulias and Kirk will vote themselves in Chicago later Tuesday morning.

Green Party candidate LeAlan Jones and Libertarian Mike Labno are also on the ballot.
And voters should keep in mind they will be voting twice for U.S. Senator. One section is for a candidate to serve the six-year term that begins in January, while the other is for an unexpired term to replace sitting Sen. Roland Burris.

Burris was appointed by since-deposed Gov. Rod Blagojevich to finish Obama’s unexpired term.

It is possible in the current election that one person could become Senator for about two months, and a different person for the following six years.

WBBM Newsradio 780 Political Editor Craig Dellimore contributed to this report.