The US state of Illinois is a Democratic stronghold and one of the "big three" Democratic states alongside California and New York.  It is considered one of the most Democratic states in the nation and following the 2018 elections, all six statewide elected offices are held by a Democrat.
Historically, Illinois was a critical swing state leaning marginally towards the Republican Party. Following Bill Clinton's election in 1992, and his victory in Illinois, the state has been realigned in favor of Democratic candidates for president, with six consecutive wins by that party, regardless of the national outcome. Traditionally, Chicago, East Saint Louis, and the Quad Cities region have tended to vote heavily Democratic, along with the Central Illinois population centers of Peoria, Champaign-Urbana and Decatur. In recent years, Chicago's suburban collar counties continue to trend Democratic as well. 
Rod R. Blagojevich, a Democrat, was elected as Illinois' Governor in 2002, replacing George H. Ryan. Blagojevich was re-elected in 2006, defeating Republican State Treasurer Judy Baar Topinka. However, in 2009, Blagojevich was impeached and removed from office due to charges that he abused his power while in office. Lieutenant Governor Pat Quinn succeeded him. Following Quinn's election to a full term outright in 2010, the state elected Bruce Rauner, the first Republican chief executive in twelve years. Following the 2018 elections, J.B. Pritzker will become the state's current Democratic governor.
|Governor||J. B. Pritzker||Democratic||2019|
|Lieutenant Governor||Juliana Stratton||Democratic||2019|
|Secretary of State||Jesse White||Democratic||1999|
|Attorney General||Kwame Raoul||Democratic||2019|
|U.S. Senator (Class II)||Dick Durbin||Democratic||1997|
|U.S. Senator (Class III)||Tammy Duckworth||Democratic||2017|
As of October 2016, Illinois had nearly 8 million active, registered voters. 
|2016||38.76% 2,146,015||55.83% 3,090,729|
|2012||40.66% 2,135,216||57.50% 3,019,512|
|2008||36.73% 2,031,179||61.83% 3,419,348|
|2004||44.48% 2,345,946||54.82% 2,891,550|
|2000||42.58% 2,019,421||54.60% 2,589,026|
|1996||36.81% 1,587,021||54.32% 2,341,744|
|1992||34.34% 1,734,096||48.58% 2,453,350|
|1988||50.69% 2,310,939||48.60% 2,215,940|
|1984||56.17% 2,707,103||43.30% 2,086,499|
|1980||49.65% 2,359,049||41.72% 1,981,413|
|1976||50.10% 2,364,269||48.13% 2,271,295|
|1972||59.03% 2,788,179||40.51% 1,913,472|
|1968||47.08% 2,174,774||44.15% 2,039,814|
|1964||40.53% 1,905,946||59.47% 2,796,833|
|1960||49.80% 2,368,988||49.98% 2,377,846|
The 2016 Presidential election featured former Secretary of State Hillary Clinton against real estate mogul Donald Trump. As expected, Clinton won Illinois handily, 56% to 39%, though Trump won the election. Illinois backed the Democratic candidate for the seventh consecutive presidential election.
Illinois' historic Chicago- downstate divide deepened even further; with Clinton winning Cook County and most of the collar counties by an even larger margin than longtime Chicago resident Barack Obama did in 2012,  while Trump's share of the vote was greater than Mitt Romney's four years earlier in all but two of the downstate counties.  As in much of the Midwest, Trump's strong performance downstate was largely propelled by the region's many white working class voters. County by county, the national shift toward the Republican Party under Trump was most pronounced in the Midwest, and enabled Trump to win every Midwestern state except Illinois and Minnesota, the latter of which he lost by only 1.5%.
The incumbent and Illinois resident, President Barack Obama faced Republican Governor Mitt Romney, of Massachusetts, in the general election. Barack Obama carried Illinois with a margin of four and one quarter points less, as a share of the total, than he did in his 2008 victory. Mitt Romney carried for points more than the preceding Republican nominee, John McCain; President Obama defeated Governor Romney in the electoral college overall, winning reelection. Obama's victory in Illinois was due to an overwhelmingly strong vote total in Cook County, which includes Illinois' largest city, Chicago. Obama won Cook County with 74%, compared to Romney who received only 24.6% of the votes in Cook County. The importance of the vote in Chicago and the rest of Cook County to Obama's victory in Illinois can be illustrated by a hypothetical scenario in which its votes are not included in the overall state total. If one were to subtract all of the votes in Cook County from Illinois' total votes cast, Romney would have actually won Illinois. The 2012 statewide victory for the Democratic candidate constitutes the sixth consecutive win by that party, regardless of national outcome.
The 2008 Presidential election featured Democratic candidate, and Illinois resident, Barack Obama facing off against US Senator John McCain. Barack Obama carried Illinois by a much bigger margin than Kerry did in 2004. Obama won Illinois with 62% of the vote. In addition to carrying major urban centers, Obama won a number of rural counties as well, a trend reflected across the country and especially the Midwest. Prior to his election to President, he represented the state in the US Senate since January 2005.
Democratic Presidential candidate John Kerry carried Illinois with 54% of the vote. His victory in Illinois was largely determined by a wide margin of votes cast in Cook County, with many counties outside of the Chicago metropolitan area voting for President Bush. Illinois politics are largely regionally divided, with Chicago and a few downstate microurban communities supporting Democratic candidates, the Chicago suburban counties being primarily "swing" or "purple" areas, and much of the rural portion of the state being conservative. Several of the notable "downstate" blue spots that contributed to Kerry's win include East Saint Louis, the Quad City region, Peoria, and Champaign and Jackson counties, which have a large college-bound population.
- "Illinois: The Most Democratic State". NBC Chicago.
- "Dem's Downstate losses offset in Collar Counties". Retrieved 12 February 2017.
- "Illinois has highest number of registered voters since 1970". chicagotribune.com. Retrieved 12 February 2017.
- Bentle, Kyle. "In Illinois, Chicago-area Clinton votes overtook rest of state". chicagotribune.com. Retrieved 17 March 2018.
- "Illinois 2016 Presidential And State Election Results". npr.org. Retrieved 17 March 2018.