By going to the closed primary system, black Democrats have become more likely to go farther in the electoral process. Recall that at present statewide whites make up only 54 percent of Democrat registrations, probably of which half routinely vote Republican in federal elections. This means among Democrats likely to vote in a party primary, blacks will outnumber whites substantially statewide. This also entails that, unless there is a large surplus of white independents relative to black independents that choose to participate in the Democrat (as opposed to the same-day Republican) primary, black candidates will win these nominations given very low proportion of black crossover votes to white candidates where there are viable white and black candidates in a contest (which is lower that rate of white crossover to black candidates).
In contrast, Republicans win out because their black opponents are likely to be more liberal than potential white opponents, and also because of crossover voting realities making these nominees less electable. Therefore, Republicans become more likely to win federal elections generally. To be more specific, regarding the present seven districts and the state:
Some observers may have wondered by a coalition of Republicans and black Democrats supported the bill that produced this change. The answer should be obvious by a review of these facts and data: black Democrats become more powerful in the party by their ability to get more nominations for federal office, while Republicans become more likely to win these offices. The biggest mystery is why Gov. Kathleen Blanco, a white Democrat, signed the bill. But there’s no mystery that, as a result, white Democrat federal officeholders will become nearly extinct, and Republicans candidates will benefit the most.