Recently the CBO issued its annual budget projection, and it's pretty benign for the next decade, then climbs at a pretty measured pace.
Yet, note that in the last recession our debt relative to GDP doubled. Given that economists still don't have a good model for predicting business cycles let alone avoiding recessions, we can expect more of them. I think the odds that we elect a modern-day Calvin Coolidge next term are much smaller than the odds the deficit will increase dramatically when the next recession hits.
Consider that in 2007, before anyone saw any hint of the 2008 crisis, the debt was actually projected to fall, but we know how that turned out (black are actual historicals). That is, they never anticipate recessions, though we all know they haven't been abolished. I pulled these numbers out of the 2007 'wayback machine' which is a great way to hold large institutions accountable, because for some reason the CBO doesn't keep their historical forecasts on their current site (maybe the NSA can get Google to scrape them away?). Liberals who happen to be economists (eg, Brad DeLong) think the latest objective projections prove we have no budget worries. I guess some people really do think This Time It's Different.