At the risk of sounding petty isn't this exactly like "as soon as Democrats are in office all of a sudden the deficit will mean something again?"
Exactly. We never heard a peep about the deficit when Repubs were enacting tax cuts for the wealthy.
In reality, there is no consensus among economists about what percentage of GNP is appropriate for the deficit, and interest rates are very low right now, suggesting that there's plenty of headroom.