We might have a clue from a Republican aide complaining Wednesday evening that the White House was going backwards on the size of the spending cuts it was willing to accept:
"Thursday it was $2 trillion, Monday it was $1.7-1.8 trillion, Tuesday it was $1.6-1.7-1.8 trillion. This morning our staff met with White House folks and the wrap-up from that meeting said that the White House is now at $1.5 trillion."
We need more evidence to be sure -- and the GOP aide's account needs to be treated with some skepticism -- but it's suggestive the White House is going with option (b). Obama's rationale would be simple and sound: The more you jerk me around, the higher the cost of reaching a deal.