For the past 6 years, Illinois' two U.S. senators have adhered to an informal "cancellation clause," by which vote of generally conservative Republican Peter Fitzgerald cancels out the vote of very liberal Democrat Dick Durbin. Gun control issues are about the only ones on which the two senators concur.

Now, with Fitzgerald retiring after only one term, it appears that Illinois will deviate, perhaps permanently, from the norm of recent years: Barack Obama is a solid favorite to win Fitzgerald's seat in November, which would mean that two liberal Democrats will represent Illinois in the U.S. Senate. With a Durbin-Obama tandem, there will be no cancellation clause.

In recent history, Illinois voters have shown a propensity for not electing two senators from the same party. In the past 54 years, Illinois had two Democrats in the Senate for 14 years (1984 to 1998), two Republicans for four years (1966 to 1970), and a split delegation for 36 years (1950 to 1966, 1970 to 1984 and 1998 to 2004).

Likewise, Illinois was a "swing" state in the past 13 presidential contests. A Republican won the state in 1952, 1956, 1968, 1972, 1976, 1980, 1984 and 1988, and a Democrat won in 1960, 1964, 1992, 1996 and 2000. Al Gore won the state in 2000 by the sizable plurality of 569,605 votes, which was only marginally less than Bill Clinton's 1996 plurality of 754,723 and 1992 plurality of 719,254.

Clearly, Illinois has moved into the realm of being a so-called "blue" Democratic state, as opposed to a "red" Republican state. In the 2000 Bush-Gore race, America had 30 red states and 20 blue states, plus the District of Columbia. George Bush amassed 271 electoral votes, to Gore's 267.

Using a red/blue matrix is instructive in projecting control of the U.S. Senate after the 2004 election. At present, the Republicans hold a 51-49 majority. Of the 30 states won by Bush in 2000, 17 have two Republican senators, six have two Democratic senators, and seven have a split delegation. Of the 20 states won by Gore, 12 have two Democratic senators, two have two Republican senators, and six, including Illinois, have a split delegation.

If the country is realigning itself, then the Republicans will augment their majority by electing more senators in red states. Of the 34 senators whose terms expire in 2004 (19 Democrats, 15 Republicans), nine of the 11 most contested seats are in red states.

In the split-delegation states of South Carolina and Georgia, a Republican is poised to win; in North Carolina, a Democrat, former Clinton chief-of-staff Erskine Bowles, is leading. Among the six red states with two Democrats, incumbents have retired in Louisiana and Florida, and Republicans have a decent chance to win both; and in South Dakota, Senate Democratic leader Tom Daschle faces a tough fight against Republican John Thune, who lost a 2002 Senate bid by just 524 votes.

Republican retirements in the red states of Colorado and Oklahoma have given Democrats unexpected openings, and Lisa Murkowski, who was appointed senator by her father, Alaska's governor, is fighting nepotism charges and may lose.

In the blue states, the only opportunity for a Republican pickup among all-Democratic delegations is in Washington, where George Nethercutt, a congressman, could upset Democratic incumbent Patty Murray. And, of course, Illinois could become a 2-D state, with Obama beating a Republican designated to replace Jack Ryan, who resigned the nomination due to allegations that he took his former wife to sex clubs.

From a Republican perspective, the loss of the Illinois seat is neither distressing nor discouraging. It's already perceived as offset by gains in South Carolina and Georgia, where two congressmen, Jim DeMint and Johnny Isakson, respectively, will win. In Louisiana, a suburban New Orleans congressman, David Vitter, is certain to finish first and make the runoff against a large field of Democrats; if a black Democrat finishes second, as is possible, Vitter is a cinch to win. In North Carolina, Bowles' Clinton connection is sure to be an issue, to be exploited by the Republican nominee, Richard Burr, a congressman from Winston-Salem. In Florida, which Bush won by a disputed 537 votes in 2000, both parties are enduring nasty primaries to pick nominees. The Republican is expected to be Bill McCollum, a former congressman who lost the 2000 Senate race by 284,039 votes; the Democrat will likely be Betty Castor, a former state education commissioner. Castor would have only a slight edge against McCollum.

The outcome of the presidential race will significantly affect the 2004 Senate contests. If voters are repelled by the president's handling of Iraq and the economy, then Republicans will lose tight races in Colorado, Florida, Alaska, Oklahoma, North Carolina, South Dakota and Louisiana, handing the Democrats a 51-49 U.S. Senate majority. If Bush surges and voters don't punish him for his Iraq decisions, then Republicans could keep all their seats except the one in Illinois, win up to six Democratic-held seats, and end up with a 56-44 majority.

As the adjoining vote chart indicates, Durbin and Fitzgerald vote differently on virtually every issue except gun control. Durbin has voted on a number of issues which, if Illinois were a red state, could cause him problems, such as opposing welfare reform extension and a ban on partial-birth abortions and supporting a pay hike and a rollback of the Bush tax cuts. But Durbin won in 2002 with 60 percent of the vote, and he now looks like a long-term political fixture in blue Illinois.

Durbin is part of the Democratic leadership, as an assistant minority whip, and he aspires to move up. If Daschle loses and Nevada's Harry Reid becomes Democratic leader, Durbin has a viable chance to become Democratic whip, the number two spot.