If you live in Butler or Warren counties in the Republican-leaning suburbs of Cincinnati, you can vote for president beginning in October by going to a polling place in the evening or on weekends. Republican officials in those counties want to make it convenient for their residents to vote early and avoid long lines on Election Day.

But, if you live in Cincinnati, you’re out of luck. Republicans on the county election board are planning to end early voting in the city promptly at 5 p.m., and ban it completely on weekends, according to The Cincinnati Enquirer. The convenience, in other words, will not be extended to the city’s working people.

The sleazy politics behind the disparity is obvious. Hamilton County, which contains Cincinnati, is largely Democratic and voted solidly for Barack Obama in 2008. So did the other urban areas of Cleveland, Columbus and Akron, where Republicans, with the assistance of the Ohio secretary of state, Jon Husted, have already eliminated the extended hours for early voting.

County election boards in Ohio, a closely contested swing state, are evenly divided between Democrats and Republicans. In counties likely to vote for President Obama, Republicans have voted against the extended hours, and Mr. Husted has broken the tie in their favor. (He said the counties couldn’t afford the long hours.) In counties likely to vote for Mitt Romney, Republicans have not objected to the extended hours.

This is just the latest alarming example of how Republicans across the country are trying to manipulate the electoral system by blocking the voting rights of their opponents. These actions have a disproportionate effect on blacks, Hispanics and other ethnic minorities who struggled for so long to participate in American democracy.

Cincinnati, for example, is 45 percent black, and Cleveland 53 percent. Butler County, however, is 8 percent black, and Warren 3.5 percent. This kind of racial disparity is clearly visible wherever Republicans have trampled on voting rights during Mr. Obama’s term.

In Florida, more than half of black voters went to the polls early in 2008 largely to support Mr. Obama. So, last year, Republican lawmakers there severely curtailed the early voting period. In Pennsylvania and other states that have imposed strict voter ID requirements, the impact will be felt hardest by blacks, Hispanics, older citizens and students, all of whom tend to lack government ID cards at a higher rate than the general population. At the trial in Pennsylvania over the constitutionality of the state’s voter ID law, the plaintiffs introduced clear evidence, compiled by a geographic data analysis firm, that registered voters in Philadelphia who lack government ID cards are concentrated in minority and low-income areas.

In Ohio, as in other states, the Republican Party is establishing a reputation for putting short-term political gain ahead of the most fundamental democratic rights.