He seems to be basing this negative opinion on the struggle in the House to get the last Defense Supplemental Bill passed. The Obama Administration claims that they will no longer request these to support continuing operations in Afghanistan and Iraq. The proposed 2010 budget contains the planned funding for these right now.
The reason the House Bill was close was that the Republicans fought it for all of the non-Defense spending added to it. Some liberal Democratic members were upset that there was no time line for ending operations in Afghanistan now that it seems the war is winding down in Iraq with the movement of U.S. troops out of the major cities. Obama is claiming this represents the first step in moving all of the troops out of Iraq. Some liberal peace hawks, like Congressman Dennis Kucinich (D-OH), aren't buying that claiming this movement is not a withdrawal, really just a redistribution of troops.
Murtha's belief is unfounded at this time. Congress will pass most of the bill submitted by the President. Right now the fights between him and Congress are over keeping big ticket production items going; not on the total amount of spending or the need for it. Murtha has used the defense budget to add money and items not necessarily requested by the military. If he remains in his powerful post he will be able to keep doing so and add to the defense budget if he desires.
Murtha does believe it will be hard to pass another supplemental for Iraq and Afghanistan if required. If it is it really is the fault of Obama and not Congress. He is the one promising no more of these types of bills, if he had not made that promise during the campaign he would not be limited in his options. Honestly right now the way things are going the 2010 elections will not favor the Democrats in the House and it may be that Murtha won't have to worry about this kind of thing. There is also the ongoing PMA investigation that also will help him in his future career decisions. One hopes at least.