When I suggested last week that Democrats wanting to survive the Obama era should stay away from the Democratic National Convention, I never imagined that the idea would catch on like wildfire. The latest is Sen.Claire McCaskill (D-Mo.). She joins lawmakers from Ohio, Pennsylvania and West Virginia in staying as far away as possible from President Obama’s moment in the sun. The National Journal reports:

If historical precedent is a guide, President Obama should be worried about the recent spate of Democrats who have declared that they won’t attend their own party’s national convention. . . .

Such defections amounted to an early alarm bell as recently as 2008, when a deluge of Republicans steered clear of the Republican National Convention lest they be associated with a then-deeply unpopular GOP. Three months later, a Democratic wave swept the White House and congressional elections.

Now Democrats are the ones abandoning ship. Already five House members — Mark Critz of Pennsylvania, Kathy Hochul and Bill Owens of New York, Nick Rahall of West Virginia and Jim Matheson of Utah — have joined Sens. Joe Manchin of West Virginia, Jon Tester of Montana, and Claire McCaskill of Missouri in deciding that they won’t attend this year’s Democratic National Convention. . . .

McCaskill “isn’t just any Dem,” Republican National Committee spokesman Tim Miller said on Tuesday in a tweet. “She was Obama’s top surrogate in ’08. Avoiding him at all costs shows just how bad it is for O out there.”

In other words, McCaskill is saying more people than not in her home state don’t like Obama. I suppose we can agree that Missouri is no longer a swing state. Moreover, by staying away McCaskill makes it that much harder for other vulnerable Democrats to stick by Obama. Why aren’t they demonstrating their independence also?

It is hard to say who will be next to bug out. Sen. Debbie Stabenow (D-Mich.) or Sen. Robert Casey Jr. (D- Pa.)? Maybe Rep. Tammy Baldwin (D-Wis.), running for the Senate in Wisconsin? These pols have no reason to flee the convention other than self-interest. If they hide from Obama and they are guided by competent pollsters, we can assume that their state is leaning against Obama.

There is lot of polling out, to put it mildly. But consider the basic incumbent rule: If the officeholder is below 50 percent, he’s in trouble. Take a look at polling averages in Ohio, Virginia, Wisconsin and elsewhere. If he’s not above 50 percent, he’s struggling, and Democratic lawmakers should consider McCaskill’s strategy. Sure, all these candidates will still have a “D” after their names, but there’s no upside in reminding swing voters of that unpleasantness.