In some states, one political party dominates even without a lift from gerrymandering.
The most extreme examples are Hawaii, Massachusetts and Rhode Island, all of which have legislatures controlled by Democrats.
Their control is so complete that in about two-thirds of legislative races in each state last fall, voters had just one ballot option: the Democratic candidate.
The percentage of races lacking major party opposition was 71 percent in Massachusetts, followed by Hawaii at nearly 69 percent and Rhode Island at 68 percent, according to a mathematical analysis by The Associated Press . Most of the unopposed candidates in each state were Democrats.
The AP examined all U.S. House races and about 4,900 state House and Assembly seats up for election last year using a statistical method of calculating partisan advantage designed to flag cases of potential political gerrymandering. The U.S. Supreme Court is hearing arguments Tuesday on a pair of cases alleging unconstitutional political gerrymandering.
