Obama threatening constitutional crisis over Syria?

Chuck Todd had previously noted that Obama might go forward with the Syria attack and that he could go forward with it even if Congress rejects authorizing the use of force.  From Fox News on Saturday night:

One senior State Department official, though, told Fox News that the president’s goal to take military action will indeed be carried out, regardless of whether Congress votes to approve the use of force. 

Other senior administration officials said Obama is merely leaving the door open to that possibility. They say he would prefer that Congress approve a military attack on the Assad regime, in response to its alleged use of chemical weapons, and will wait to see what Congress does before making any final decisions on authorizing military force. . . . 

“That’s going to happen, anyway,” the source told Fox News, adding that that was why the president, in his Rose Garden remarks, was careful to establish that he believes he has the authority to launch such strikes even without congressional authorization. . . . 

Does the president really think that he will be more likely to get approval if he makes these threats?  Isn't he worried that out of principle Congress will reject his demands since they don't want to let a president "blackmail" them via threat of constitutional crisis?