If the PRD candidate loses, would it damage Lopez Obrador standing (is that the right word to use?) at all?
Hard to say. It shouldn't have much immediate effect on either the lawsuites or his protests, but it will have longer-term effects both on his party's strength and the internal politics within it.
At present PRD controls governorships in Guerrero, Zacatecas, Michoacan, Baja California Sur and Mexico City. Technically, it is not in sole control of Chiapas, though the governor has moved in their direction. If they control Chiapas fully and win (as they most surely will) Tabasco in October, this creates a fairly solid "PRD South" - of the four southernmost states, they'd cotrol all but Oaxaca (and, quite likely, they'd get that state soon as well - if the striking teachers manage to depose the PRIista governor there, as they seem to be likely to do).
It should be also noted that the three PRD-governed non-southern states are not really "Obradorista", since PRD control there predates Lopez Obrador's ascendancy within the party. Michoacan governor Lazaro Cardenas is the son of Cuahutemoc, and has been fairly transparently distancing himself from Lopez. I expect him to endorse the Electoral Tribunal verdict no matter what it is and no matter what Lopez does. In fact, it is almost inevitable that the young Cardenas either challenges Lopez Obrador for leadership or defects within the next 6 years (I expect him to do both). In Michoacan, as well as in Zacatecas and in Baja California Sur, Lopez didn't do any better (in some areas, he actually did worse) than his party's congressional candidates. In fact, these are, pretty much the only states where this was the case: he seems to have no personal vote there, so the local party leaders are entirely free to be independent.
In contrast, the "Southern PRD" is Lopez Obrador's creature. It is there that the PRD managed to benefit the most from PRI defections that he's been able to engineer. Most local PRD leaders and regulars were PRIistas, until they switched under Lopez Obrador's influence (in fact, their candidate in Chiapas was himself a PRIista until very recently). Thus, to the extent that PRD becomes the governing party in the South, it is strengthening Lopez, first and foremost.
Now, of course, success in the South also means weakening of the Cardenistas within the party. If the young Cardenas defects or is pushed out, his father will also bolt (so far, the only thing that seems to holding the old guy is the hope he has that in 2012 his son will get the party's nod for presidency). This, in turn, would mean weakening of the party in its traditional strongholds, but the Southern states, in any case, are, in general, juicier and more populous targets, so, even on the ballance, PRD might be better off. As for Lopez, there is no doubt that he needs the "southern strategy" to succeed - otherwise, the Cardenista challenge against him within the party might be viable.
PAN never had a chance in Chiapas, so they made a right decision. Aside from avoiding an inevitable beating at the polls with all the accompanying headlines, if PRI candidate wins, they manage to screw Lopez also within the PRD. Even though Cardenista wing of PRD is, in a way, the more consistently leftist and ideological in their convictions, there is no real enmity between them and PAN. In part this is due to the fact that PANistas and Cardenistas were allies in their fight against the old PRI regime, so their leaders feel some degree of mutual friendship, even personally. Furthermore, Cardenista de facto "non-participation" in the Lopez campaign means that the two groups have done nothing to offend each other over the last year. At present PANistas feel they can deal with the Cardenistas, whereas the Obradoristas are going to be implacable foes for the next 6 years. Thus, anything they can do to weaken PRD in the South not only weakens their main opponent, but also makes it more likely that they would face the relatively friendly Cardenista PRD accross the isle nationally. Smart.
