The Center on Budget and Policy Priorities has a new report out comparing how the Obama administration's budgetary changes have, and would project to, effect the deficit. This chart sums it up:

(This figure uses Office of Management and Budget numbers because the Congressional Budget office's analysis has not yet come out. The CBO-based figures ought to be similar.)

Conservatives tend to get very upset when it's pointed out that policies and economic conditions that predate the Obama presidency entirely -- indeed, more than entirely -- account for the deficit over the next decade. So let me concede that this fact does not end the debate about how to proceed going forward. As CBPP puts it:

According to the Administration’s own estimates, its budget would reduce deficits by $2.1 trillion over the 2011-2019 period — or (more appropriately) by $1.2 trillion, when using a baseline that (like CBPP’s) assumes a gradual phasedown of operations in Iraq and Afghanistan and does not count future reductions in costs there as lowering the deficit. (See Figure 2.) The Congressional Budget Office and the Joint Committee on Taxation are currently sifting through President Obama’s budget proposals, and we await the results of that analysis. Although the Administration and CBO figures will certainly not match exactly — for a variety of economic, technical, and conceptual reasons — it is clear that, using a reasonable benchmark, the President’s budget proposals would reduce future deficits by a significant amount.
Like most fiscal analysts, we believe that the Administration and Congress will need to take considerably larger steps. The President himself acknowledges that his proposals do not fully put the budget on a sustainable footing and is establishing a bipartisan fiscal commission to recommend more substantial deficit reductions.

Still, the political reality is that Republicans have had enormous success in convincing people that the Obama administration has caused the dire fiscal situation. Correcting that untruth is worthwhile.