The already dwindling Blue Dog Coalition of centrist House Democrats will shrink to even fewer members thanks to the 2014 midterm elections.

In two of the biggest upsets of the night, Blue Dog Reps. John BarrowJohn Jenkins BarrowOur democracy can’t afford to cut legal aid services from the budget Dem files Ethics complaint on Benghazi panel Barrow thanks staff in farewell speech MORE (D-Ga.) and Nick RahallNick Joe RahallWe shouldn't allow politics to impede disaster relief Break the cycle of partisanship with infant, child health care programs Clinton mulls role in 2018 midterms MORE (D-W.Va.) lost reelection.

Rep. Pete Gallego (D-Texas) also lost, while Rep. Jim Costa (D-Calif.) was trailing in a race still too close to call on Wednesday. Meanwhile, Rep. Ron Barber (D-Ariz.) was tied in his race against retired Air Force Col. Martha McSally (R).

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Barrow's defeat was especially significant because he was the last white House Democrat representing a district in the Deep South. The five states that make up the Deep South region are Alabama, Georgia, Louisiana, Mississippi and South Carolina. 

The region's surviving Democrats are all African-Americans who represent largely black districts. 

Like other white Southern Democrats before him, Barrow repeatedly had been able to cobble together a winning coalition of black voters and white conservatives, but he was unable to survive a particularly difficult year for his party, in which the country's first black president, Barack Obama, weighed down the ticket.

"I think this is another sign of the continuing racial polarization of the electorate," said John McGlennon, a professor at the College of William & Mary who specializes in the politics of the South. "Barrow really was the last man standing who had been able to withstand trends, partly because of the imaginative campaigning and weak opponents. At some point, though, even his number was up." 

Barrow managed to cling to his seat, despite representing a conservative district with his retail politicking skills and folksy appeal. One infamous 2012 campaign ad featured Barrow showcasing his guns, including his grandfather's Smith & Wesson that he had used "to help stop a lynching."

While Barrow has been a perennial GOP target, Rahall, a 19-term incumbent who is the top Democrat on the House Transportation and Infrastructure Committee, hadn't faced such a tough race in decades.

Rep. Kurt SchraderWalter (Kurt) Kurt SchraderDems reverse course on White House parks plan Overnight Energy: EPA watchdog won’t drop Pruitt probes | Exxon leaves conservative advocacy group | Lawmakers offer changes to Endangered Species Act Western lawmakers introduce bills to amend Endangered Species Act MORE (D-Ore.), a co-chairman of the Blue Dog Coalition, said the losses of Barrow and Rahall highlighted the challenges for Democrats this cycle.

"Those states have been trending more Republican over the last decade," Schrader said of Georgia and West Virginia. "It's a testament to Nick and John they lasted that long."

Schrader noted that many centrist Republicans won reelection Tuesday night, suggesting that Democrats should moderate their message in order to appeal to more voters, such as signaling openness to deficit reduction, business tax reform and limiting regulations.

"I don't think setting the president up for a lot of vetoes will resonate with the American people," Schrader said of the upcoming GOP-controlled Congress.

The retirements of Reps. Jim Matheson (D-Utah) and Mike McIntyre (D-N.C.) earlier this year, as well as Rep. Mike Michaud's (D-Maine) run for governor, already meant there would be fewer Blue Dogs in the next Congress. Just two Blue Dogs in competitive races, Reps. Cheri Bustos (D-Ill.) and Collin Peterson (D-Minn.), managed to hang on Tuesday night.

At least two new House Democrats are expected to join the ranks of centrists: attorney Gwen Graham, who defeated Rep. Steve Southerland (R-Fla.), and Brad Ashford, who is currently leading over Rep. Lee Terry (R-Neb.) in a race still too close to call.