Basically anyone with a pulse is taken seriously by our media if they run for president as a Republican. I don't see one this week, but the NYT has run weekly fawning profiles of all the wannabees - even before they declared! - over the past couple of months. If you're a Democrat, however, and you're slightly to the left of Jeb Bush, you aren't "serious."
I ain't gonna bet on Bernie Sanders winning the nomination, but I wouldn't bet on Jindal, Perry, Christie, etc... either.