A useful definition of a wedge issue is one that unifies a party while splitting the opposition.
By that definition, Republican calls to impeach President Obama look like a wedge issue — in favor of Democrats. As a recent CNN poll shows, 65 percent of Americans oppose impeaching Obama, including 86 percent of Democrats, 63 percent of independents and even 42 percent of Republicans.
Given those numbers, no one should be surprised that Democrats are playing up the possibility of impeachment.