Thirteen states have voted for Republicans in every presidential election since 1980: Alabama, Alaska, Idaho, Kansas, Nebraska, North Dakota, Mississippi, Oklahoma, South Carolina, South Dakota, Texas, Utah and Wyoming. This track record makes them the most consistently safe Republican strongholds in modern presidential politics.
In 1988, these states' turnout barely trailed that of the rest of the country, by 2.56%. But in every election since, these 13 states have fallen further behind. In 2008, their turnout was 6.22% behind the rest of the nation.
Meanwhile, the safest Democrat states (the 12 states that went for Obama in 2008 by more than 10% and for either Kerry or Gore by more than 10%) have experienced a similar trend as turnout lessened compared to the rest of the country in each election from 1988 to 2004 (although their turnout started off higher than the safest Republican states).
Our findings should come as no surprise. Under the Electoral College system as currently constituted, people vote for president at the state-level. Once all votes are tallied in a state, the winner of the statewide popular vote receives all of the state's electoral votes. This is known as the winner-take-all rule, in place as a statute in 49 of the 51 states (including the District of Columbia, which has electors).