Obama almost always cleans up at caucuses, so Hillary's team is attempting to find a way to argue that the popular vote is all that matters. As Glenn Smith writes, Hillary's team hopes,
... that if they win the popular vote, they can avoid, at least for one news cycle, news reports that even if they do so they will very likely lose the delegate fight in Texas and fall further behind Obama in the national delegate contest.
This is not speculation. This has been the subject under discussion. While I have not been part of that discussion, plenty of sources last night and this morning confirmed this as the core of the dispute.
It is widely assumed that Obama's organizational advantage will achieve in the caucus portion of the Texas election just what it has achieved in earlier caucuses: a significant victory in delegates. There are 67 delegates at stake in those caucuses. The Clinton campaign would like to delay the reporting of the caucus results, and that is why they have continually "reserved the right to challenge" Texas law and Democratic party procedures.
If Hillary wins Ohio -- and the popular vote in Texas, that might be enough to keep her in the race -- even if she techically loses Texas (due to the caucus). She could then argue to Super Delegates that she -- having won the popular vote in both Ohio and Texas -- is the candidate with momentum. It's a stretch, but this is clearly her plan ...