McIntyre was preparing for a rematch with the guy who'd nearly defeated him, state Sen. David Rouzer, though recently, another Republican, New Hanover County Commissioner Woody White, had also started expressing interest in a bid. Regardless of his opponent, McIntyre would have faced an incredibly difficult re-election effort, especially since Democratic turnout typically drops in midterm years.
McIntyre's fundraising in the most recent quarter was a bit soft, and there's a good chance he was staring at polls that showed he couldn't pull off another death-defying win. And given the district's demographics, this seat—the third-reddest held by a Democrat—is almost certain to flip to Republicans this fall.
McCarthy's seat, though, is likely to stay in Democratic hands. McCarthy first won office in 1996 by beating a Republican incumbent on the strength of her gun safety advocacy: Her husband was murdered and her son badly wounded in an infamous mass shooting on the Long Island Rail Road in 1993. McCarthy had handily won re-election in recent years, though she survived a bit of a scare during the GOP wave of 2010.
Last year, though, she announced that she had lung cancer, which she described as "treatable," so her decision to call it quits is not a major surprise. And even though the 4th District actually became a bit redder after redistricting (thanks to a federal court, not vindictive political opponents), Obama still carried it by a 56-43 spread. That puts it at the outer edge of what Republicans are capable of winning, giving Democrats a strong chance to hold it.
McIntyre's retirement is ultimately the bigger deal, since his departure will make it harder for Democrats to retake the House. (If there's a silver lining for progressives, it's that there'll be one fewer ideological outlier in the Democratic caucus.) But Democrats will also probably find themselves expending resources to hold McCarthy's seat that they might not have had the incumbent chosen to seek re-election, though these kinds of retirements are part of the expected ebb and flow for both parties every cycle.
As always, we'll be following all future developments in both seats closely, so stay tuned to Daily Kos Elections.