For 70 years following the Civil War, a majority of Iowa voters supported the Republicans over the Democrats in nearly all state and national elections. During the Great Depression of the 1930s, Iowa briefly turned to the Democrats, supporting Franklin D. Roosevelt in two presidential elections. But from 1940 through 1992, the majority of Iowans voted Republican in 10 of 12 presidential elections. Republicans won 34 of the 42 gubernatorial elections from 1900 through 1990 and controlled both houses of the state legislature for 112 of the 130 years from 1855 to 1984.
In the 1960s, Iowa showed signs of a Democratic upsurge. Harold Hughes, a liberal Democrat, revitalized the party in Iowa and was elected governor for three two-year terms before moving on to the US Senate. During the post-Watergate period of the mid-1970s, Democrats captured both US Senate seats, five of the six congressional seats, and both houses of the Iowa legislature.
By the early and mid-1990s, a balance had reasserted itself. In 2000, Iowa gave Democrat Al Gore 49% of the vote, while Republican George W. Bush received 48%, and Green Party candidate Ralph Nader picked up 2%. In 2002 there were 1,966,459 registered voters. In 1998, 32% of registered voters were Democratic, 33% Republican, and 35% unaffiliated or members of other parties. The state had seven electoral votes in the 2000 presidential election.
Republican Terry Branstad won election to a fourth term as governor in 1994. But in the 1998 election he was succeeded by Democrat Tom Vilsack, who won reelection in 2002. As of 2003, a Democrat and a Republican both served in the US Senate—Republican Charles Grassley, who won election to a fourth term in 1998, and Democrat Tom Harkin, who won reelection in 2002. In the 2002 elections, Iowans sent four Republicans and one Democrat to represent them in the US House. In mid-2003, there were 29 Republicans and 21 Democrats in the state senate, and 54 Republicans and 46 Democrats in the state house.
Iowa's presidential caucuses are held in January of presidential campaign years, earlier than any other state, thus giving Iowans a degree of influence in national politics.