For example, Obama is putting a lot of the onus today on Speaker John Boehner (R-OH) to get his caucus in line while at the same time calling Boehner a reasonable, well-intended guy that Obama can do business with. That ratchets up the pressure on Boehner in excruciating and unpleasant ways -- it also drives a stake into the fissure in the GOP conference -- while costing Obama absolutely nothing politically and probably works to his political advantage if the press picks up that theme in its coverage.
I'm oversimplifying a bit but if you look at Obama's rhetoric on the debt ceiling fight, it's been heavily weighted toward how reasonable he is being. And that hasn't worked very well. Today he's shifted his tone more to how unreasonable the Republicans are being. That has a chance to get some traction, maybe not with voters but DC media. He badly needs that narrative to stick -- and the fact that is an accurate and true narrative means it's on him to make it stick. This presser is at least a step in that direction.