Illinois, in the prevailing political vernacular, is a "blue" -- meaning Democratic -- state, and it is getting inexorably bluer. The reasons are threefold: demographics, dysfunction and disillusionment.

Those three factors are especially prevalent in the Collar Counties surrounding Chicago: DuPage, Kane, Lake, McHenry and Will. Once bedrock Republican, they are now peat moss. The Republican Party has collapsed in Will County, and it is in advanced stages of atrophy in the others.

For Republicans, Illinois' political trajectory is beyond ominous; it's positively lethal. Minorities are solidly Democratic. Fiscally conservative suburbanites, who should vote Republican but who are anti-gun rights, pro-abortion rights and pro-gay rights, have embraced the Democrats. Even conservative Democrats, particularly union members, support liberal Democrats because they view the Republicans as elitist.

Republican Richard Nixon won Illinois over Democrat George McGovern in 1972 by 2,788,179-1,553,872, winning by a margin of 874,707 votes and getting 59 percent of the vote. Ronald Reagan won the state in 1980 over Jimmy Carter by 2,358,049-1,981,413, winning by 376,636 votes and getting 50 percent of the vote, with Independent John Anderson getting 7 percent.

George H.W. Bush lost Illinois to Bill Clinton in 1992 by 1,734,096-2,453,350, losing by a margin of 719,254 votes and getting 34 percent of the vote, with independent Ross Perot getting 16.6 percent. In 20 years the state's Republican presidential vote plummeted by more than one million. George W. Bush lost Illinois to Al Gore in 2000 by 2,019,421-2,580,026, losing by 569,605 votes and getting 43 percent of the vote. Republican John McCain was crushed by Barack Obama in the state in 2008, amassing 2,031,179 votes (nearly the same as Bush in 2000), to the Democrat's 3,419,348 votes, losing by 1,388,169 votes and getting 38 percent of the vote.

In the past 40 years Illinois' population has increased only marginally, from 11,113,976 in 1970 to 12,419,293 in 2000, with a 2007 census estimate of 12,783,049. According to census statistics, from 1970 to 2007 the portion of the state's population that is black grew from 13.0 percent to 14.6 percent, the Hispanic population grew from 3.0 percent to 14.6 percent, and the white population dwindled from 82.0 percent to 65.3 percent.

Cook County, including Chicago, has been the Republicans' biggest disaster. Nixon won the county by 171,039 votes and the suburbs by 341,043 in 1972. Reagan lost the county by 268,010 votes in 1980, but he won the suburbs by 210,185 votes. The elder Bush lost the county by 644,233 votes in 1992, and he lost the suburbs by 50,933 votes. The younger Bush lost the county by 746,005 votes in 2000, and he lost the suburbs by 141,076. McCain lost the county by 1,141,288 votes in 2008, and he lost the suburbs by 326,948 votes.

Why this gargantuan turnabout? Simply, demographic change. A black exodus from Chicago into the western suburbs (Maywood, Hillside and Bellwood) and southern suburbs (Harvey, Robbins, Dolton, South Holland, Homewood, Hazel Crest and Chicago Heights) prompted white residents to flee to the Collar Counties. The burgeoning Hispanic population on the Southwest Side blocked black expansion, as Hispanics moved west into Cicero, Berwyn, Melrose Park and Stone Park, again pushing whites into the Collar Counties. From the 1970s onward, Hispanics also settled in Waukegan, Elgin, Aurora and northeastern DuPage County (Addison, Wood Dale), and that population now is quite substantial.

The Republicans have been unable to capitalize on racial tensions between blacks and Hispanics. Both vote almost monolithically Democratic. Likewise, younger white voters, gays and social-issue activists on the Lakefront and in suburbs such as Evanston and Oak Park vote overwhelmingly Democratic. McCain got 32.4 percent of the suburban Cook County vote and 14.1 percent of the Chicago vote in 2008. That's not embarrassing; it's irrelevant.

Over the past 20 years that trend has spread to the Collar Counties. The explosive growth of the Hispanic population (and, to a lesser extent, the black population) has established Democratic enclaves in Lake, Will and DuPage counties. The movement of independent white voters into Elmhurst, Naperville and the Mokena-Frankfort-New Lenox area and of Jewish voters into Buffalo Grove and eastern Lake County has undermined Republican dominance.

Here's an analysis:

DuPage County: Once upon a time the DuPage County Republican machine was awesome. Nixon won by the county in 1972 by 115,298 votes, in a turnout of 229,384, capturing 75 percent of the vote. Reagan won in 1980 by 113,317 votes, in a turnout of 251,299, getting 72.5 percent of the vote. Bush won in 1992 by 63,707 votes, in a turnout of 292,835, with 60.8 percent of the vote. The younger Bush won in 2000 by 48,487 votes, in a turnout of 353,587, with 56.9 percent of the vote. McCain lost to Obama in 2008 by 45,072 votes, in a turnout of 412,324, getting 44.6 percent of the vote.

There is a clear trajectory: The number of voters has almost doubled since 1972, and virtually all of the new voters are Democrats. The Republican presidential vote in those five elections was 172,341, 182,308, 178,271, 201,037, and 183,626, respectively, a solid but stagnant base. The Democratic presidential vote soared from 57,043 in 1972 to 228,698 in 2008, a fourfold increase.

The Republicans still control all the levers of county government, including board chairman, state's attorney, sheriff, assessor, clerk of court, recorder, county clerk, treasurer and 12 of 18 county board members. That gives them a patronage army. All of the 14 state legislators elected from within the county, are Republican, but some just barely.

The northeast quadrant of the county, specifically Addison, Wood Dale and Itasca, has an exploding Hispanic population, and they vote Democratic. The area's state representatives, Franco Coladipietro (R-45) and Dennis Reboletti (R-46), won in 2008 by 1,874 and 964 votes, respectively. In the southwest, Naperville is a Republican trouble spot, with plenty of independents. Darlene Senger (R-96) beat well funded Democrat Dianne McGuire in an open seat contest in 2008 by 641 votes.

The bottom line: DuPage County used to give every Republican a 100,000-vote margin. DuPage resident Jim Ryan won by 79,633 votes for governor in 2002, and State's Attorney Joe Birkett won the county by 94,941 votes over Lisa Madigan in the race for attorney general. However, Judy Baar Topinka won in 2006 by just 31,079 votes. The Republican-controlled vote is around 200,000. If turnout in November exceeds 300,000, the Democrats will benefit statewide. Expect a lower turnout, and a 75,000-plus Republican win in the county.

Will County: The south suburban area is now heavily Democratic, with Democrats occupying every county office. Vast numbers of South Side Chicago and south suburban Democrats have moved into the county, and they have kept their affiliation.

The county went for Nixon in 1972 by 26,833 votes in a turnout of 98,788, giving him 67.0 percent of the vote. It went for Reagan by 27,335 votes (62.3 percent). It went for Clinton over Bush by 1,296 votes, but in 2000 it went for Bush over Gore by 4,926 votes. Obama won the county by 37,809 votes in a turnout of 283,003, with 56.6 percent of the vote.

In those 36 years, turnout has tripled, reflecting population growth. Now every state legislator from Will County is a Democrat. Aurora has a huge Hispanic population, which gives the Democrats a reliable base. The bottom line: Middle class whites, despite their rural and semi-suburban residency, have rejected the Republicans. The outlook: the Republicans may come close to breaking even in 2010.

Lake County: Once an enclave of upscale WASP Republicans, the county is now on the brink of partisan realignment. The portion of the county east of Route 21 from Lake-Cook Road to Route 176, encompassing Deerfield, Riverwoods, Highland Park, Lincolnshire and Bannockburn, plus Buffalo Grove and Long Grove to the west, has a significant Jewish population and is liberal and Democratic. Just north, Lake Forest and Lake Bluff are still Republican.

Waukegan, Zion and North Chicago, with minority populations, are Democratic, and the suburbs west of Interstate 94, including Libertyville, Mundelein, Vernon Hills, Lake Zurich, Wauconda, Grayslake, Round Lake Beach, Fox Lake, Lindenhurst and Antioch, are solidly Republican.

The county went for Nixon 1972 by 44,636 votes, for Reagan in 1980 by 48,063 votes, for Bush in 1992 by 17,307 votes, for Bush in 2000 by 5,930 votes, and for Obama in 2008 by an astounding 58,697 votes, giving him 59.9 percent of the vote in a turnout of 295,787. That's a definite trend, with even the western portion of the county embracing the Democrats.

However, the Republicans control most county offices, including state's attorney, clerk of court, treasurer and county clerk, and the Democrat who was elected sheriff in 2006, Mike Curran, has switched to the Republicans. The recorder and the coroner are Democrats.

Lake County's Republican base vote is about 100,000. When turnout balloons to near 300,000, the Democrats triumph. Six of the county's 11 state legislators are Democrats.

The bottom line: To win statewide, the Republicans need a 50,000-vote bulge in Lake County.

McHenry and Kane counties used to deliver Republicans majorities of 25,000 votes and 20,000 votes, respectively. In 2008 they went Democratic by 7,443 votes and 22,793 votes.

My prediction: The Collar Counties delivered Republican pluralities of 252,501 in 1972, 249,311 in 1980, 107,401 in 1992 and 97,626 in 2000, but they went Democratic by 171,814 votes in 2008. If the Republicans don't win those areas by at least 225,000 votes in November, they'll lose every statewide office.