Jim Geraghty lays out the case from a Louisiana pro. I’ll bet you didn’t know that Louisiana had a convoluted caucus last night, but they did, and “Undecided/Pro-Life” took a plurality of the caucus portion of the slate. Louisiana’s system is a bit more-complicated than that, with a combination of an Iowa/Nevada-style caucus to determine who goes to the state convention to decide who goes to the national convention (held last night) and a primary to be held on February 9. Like Iowa and Nevada, all of the delegates are supposedly “uncommitted” (at least at this point); however, not only are they expected to follow the will of the caucus-goers, but should a candidate get a majority in the primary, 20 of the 47 delegates are bound to support the primary winner, with the other 27 still officially “uncommitted”.
As an aside, both “Undecided/Pro-Life” (largely FredHeads, according to multiple sources in multiple campaigns, important because Thompson did put at least some resources in Louisiana) and John McCain (who did nothing) did better than Ron Paul (who did make a last-minute appearance).