Oakland County was historically a bastion of suburban conservatism, and was hence a longstanding stronghold of the Republican Party. However, in the 1990s it became highly competitive, and since 2008 it has increasingly shifted Democratic, giving over 50% of its votes to the Democratic candidate for president in each election. Republican strength is concentrated in the many exurban townships of the county, while Democratic strength is concentrated in suburbs such as Royal Oak, Farmington Hills, West Bloomfield, and Southfield. Some suburbs, such as Novi, Troy, Birmingham, and Rochester, were historically strongly Republican but are now relatively split between the two parties, with younger adults tending to support Democrats and older residents tending to support Republicans.

In 1996, Bill Clinton became the first Democrat to carry Oakland County since Lyndon Johnson in 1964, and only the fourth to do so since 1892. Al Gore and John Kerry also carried the county, by narrow margins, against George W. Bush in 2000 and 2004, respectively. In 2008, the county swung significantly to Barack Obama, who became the first Democrat to win a majority in the county since LBJ, and only the third to do so since 1884. (See table at right.) He again carried the county in 2012, though by a smaller margin. Hillary Clinton won a narrow majority in 2016. In 2020, Joe Biden won 56 percent of the vote. He received over 400,000 votes, and became the first Democrat to carry the county by a margin of over 100,000 votes.

While the Democratic Party has found increasing success in presidential elections in Oakland County, the state Republican Party has remained strong in some recent gubernatorial and state elections. The county favored Republican Rick Snyder by a 22-percent margin in the 2010 Michigan gubernatorial election and again by a 12-point margin in the 2014 election; conversely, Democratic candidate Gretchen Whitmer carried the county by 17 points in the 2018 race. Republicans held a majority on the County Commission for most of its history, but following the 2018 elections, Democrats won a narrow 11-10 majority on the commission.