But now, supporters of strict voter-ID, registration and other voting laws are trying to use the same defense they have used to defend gerrymandering. They can claim ostensibly good reasons for their laws: preventing fraud or saving money. As a fallback, they can claim, like Texas, they are engaged in permissible partisan discrimination, not impermissible race discrimination.

But this is specious. First, it is artificial to separate race and party under current political conditions. When Don Yelton, a Republican official in North Carolina, recently told “The Daily Show” that if the state’s strict new voter-ID law “hurts a bunch of lazy blacks,” then “so be it,” it was easy to see old-fashioned Southern racism. But just as significant was Mr. Yelton’s saying that the new law “is going to kick the Democrats in the butt.”

Second, courts should alleviate unnecessary burdens on voters whatever the state’s asserted motive. The Supreme Court has said that, in redistricting, it cannot distinguish between permissible partisan considerations (for example, grouping “communities of interest”) and unconstitutional gerrymandering. But outside redistricting, partisanship has no place. Our elections should be conducted such that all eligible voters (and only eligible voters) can easily register, and cast a vote that will be accurately counted.

Few states will be as bold as Texas and admit naked partisanship. Most will engage in polite obfuscation.

Federal judges should see through these cynical pretexts. They should hold that when a state passes a law that burdens voters, it must demonstrate, with credible evidence, that the burdens are justified by a good reason and that the laws are tailored to their intended purpose. When North Carolina says it needs a strict voter-ID law to prevent fraud, courts should be skeptical, both because such laws haven’t been found to stop much impersonation fraud (there isn’t a lot) and because the same law eased absentee voting, which increases the risk of fraud.

Shifting the debate away from the “race versus party” question toward protecting voters has many virtues. The Supreme Court isn’t interested in expanding race-based remedies these days, and the Justice Department’s suits against North Carolina and Texas face an uphill battle. Yet the justices might well find a voter protection principle appealing. In 2012, lower courts started to push back against Republican overreach in voting laws. Richard A. Posner, a federal appellate judge in Chicago, recently expressed doubts about having upheld Indiana’s voter-ID law, which he now sees as a means of voter suppression. The pivotal swing vote on the Supreme Court, Justice Anthony M. Kennedy, also seems troubled by partisan considerations in state election law.