Democrats have abandoned Senator Mary Landrieu of Louisiana, who is in a tough runoff election. (Tough is the mild way of putting it. Polls show her down by double digits to her Republican opponent.)Not only has the Democratic Party pulled its financial support for her campaign, but this week Senate Democrats refused to rally around her push for passage of the Keystone XL pipeline bill.

Maybe Democrats are simply giving up on Landrieu. Or maybe it’s something bigger: They’re giving up on the South, at least in the short term.

This region has become so solidly Republican, particularly since President Obama was elected, that there isn’t much left there for the Democratic Party to defend or salvage. For instance, prior to the 2010 midterms there were 54 Blue Dog Democrats in Congress. In the outgoing Congress, there are only 19 left, including eight from the South.

And Republican gerrymandering has further weakened Democratic power, even when Democrats vote in high numbers. As Lee Fang wrote this month at Republic Report, “Republican gerrymandering means Democratic voters are packed tightly into single districts, while Republicans are spread out in such a way to translate into the most congressional seats for the G.O.P.”After the midterms, The Associated Press provided this tally:“In January, the G.O.P. will control every governor’s office, two U.S. Senate seats, nearly every majority-white congressional district and both state legislative chambers in North Carolina, South Carolina, Georgia, Alabama, Tennessee, Mississippi, Arkansas and Texas.”It is important and relevant that The Associated Press pointed out the racial dichotomy because, in the South, ideology and racial identity are nearly inseparable.

I’m reminded of the story that one of my brothers told about being transferred along with a white co-worker to Mississippi. He and the co-worker were shopping for homes at the same time. The co-worker was aghast at what he saw as redlining on the part of the real estate agent, who never explicitly mentioned race. When the coworker had inquired about a neighborhood that included black homeowners, the agent responded, “You don’t want to live there. That’s where the Democrats live.” The co-worker was convinced that “Democrats” was code for “black.”He may well have been right. Mississippi is among the most racially bifurcated states politically, with one of the highest percentage of black voters in the country. In 2012, 96 percent of blacks voted for the Democratic presidential ticket, according to exit polling data, while 89 percent of whites voted for the Republican ticket.

Landrieu’s Louisiana isn’t much different. In 2012, Obama won only 10 of the state’s 64 parishes. Most of the 10 had a majority-black population, and the rest had black populations approaching 50 percent. Earlier this month, Landrieu got 94 percent of the black vote but only 18 percent of the white vote.

Pat Buchanan has echoed The Associated Press in his assessment of the near complete political and racial divide in the South, writing last week, “South Carolina, Georgia, Alabama, Mississippi, Louisiana and Arkansas will not send a single white Democrat to Congress, if Mary Landrieu loses her runoff. The only Democrats in the House from Deep South states will be African-Americans.”As Gallup pointed out in March, “Whites have become increasingly Republican, moving from an average 4.1-point Republican advantage under Clinton to an average 9.5-point advantage under Obama.”And this increasingly homogenous Southern delegation is likely to wield increased influence, as The Associated Press points out:“In Washington, Senate Republicans haven’t parceled out leadership assignments, but Southerners figure prominently among would-be major committee chairmen: Mississippi’s Thad Cochran (Appropriations); Alabama’s Jeff Sessions (Budget) and Richard Shelby of Alabama (Banking, Housing and Urban Affairs); Bob Corker of Tennessee (Foreign Relations); Richard Burr of North Carolina (Intelligence); Lamar Alexander of Tennessee (Health, Education, Labor and Pensions); Johnny Isakson of Georgia (Veterans Affairs).”Furthermore, many of the likely most talked about Republican presidential candidates are from the South: Jeb Bush, Ted Cruz, Bobby Jindal, Rand Paul, Rick Perry, Marco Rubio and Mike Huckabee.

The degree to which the South remains solidly Republican may well depend on the changing racial composition of Southern states, specifically a rise in their non-white population.

According to the Census Bureau, six of the 10 states with the largest “black alone-or-in-combination populations” in 2010 were Southern states: Florida, Texas, Georgia, North Carolina, Maryland and Virginia. And the four that experienced substantial growth between 2000 and 2010 in their black alone-or-in-combination populations were all Southern: “Florida grew by 29 percent, Georgia by 28 percent, Texas by 27 percent and North Carolina by 21 percent.”In addition, as the Pew Research Center’s Hispanic Trends Project pointed out last year, nine of the 10 states with the fastest-growing Hispanic populations were also in the South: Alabama, South Carolina, Tennessee, Kentucky, Arkansas, North Carolina, Mississippi, Maryland and Georgia.

This regional hyper-racialization of our politics has many origins, some historical and some current, but it does not bode well for the future of the country as a whole.

We are self-sorting ourselves into hardened, impenetrable citadels of ideological sameness that harks back to the nation’s darker days.