A registered republican voter in the United States who has decided to cross over to the other party, the Democratic party, during the primary voting season of 2008 and vote for Democratic candidate Barack Obama for President of the United States.
"Eisenhower is one of a small but symbolically powerful group of what Obama recently called "Obamacans"—disaffected Republicans who have drifted away from their party just as Eisenhower Democrats did and, more recently, Reagan Democrats in the 1980s."
- Newweek magazine By Richard Wolffe | Newsweek Web Exclusive, Feb 1, 2008
A traditionally Republican voter in an open-primary state who crosses party lines on primary-election day for the sole purpose of skewing the balance of delegates to the 2008 Democratic National Convention toward Barack Obama, not because they support the notion of an Obama presidency but because they dread the notion of a Hillary Clinton presidency; a Republican short-term infiltrator into the 2008 Democratic primary process whose mission it is to stack the deck in favor of the weaker and/or less objectionable Democratic candidate in order to eliminate the stronger candidate from the running and then continue with business as usual, voting for the Republican candidate in November.
The sign on the precinct door read, "Attention Republicans: You can become an 'Obamacan' for a day! Ask for a Democratic ballot and get Hillary out of the picture NOW. You're free to vote Republican as usual in the November election."