Republicans who choose not to vote in their party's own primary when that contest is largely predetermined; but to vote in the Democratic Primary for the purpose of causing the Democrats to be stuck with running an nonviable or badly mauled candidate in the general election. They are "feckless voters" and "fake Democrats" for the primary election who plan to vote for the Republican candidate in the general election. This strategy can backfire if the Republicans choose the "wrong" candidate in their primary, and the Democrats can use the same strategy in reverse to produce a nonviable Republican candidate for the General Election.
The Dummycrats tried to use Hillary Clinton to harrass Obama in `08, and the Dems tried to get revenge with Santorum in 2012.
by Former Wyeth Again March 18, 2013