I recently took part in a panel discussion in which the moderator asked how this recession and the policy measures taken to address it would look if John McCain, rather than Barack Obama, had been elected president.

It’s always hard to imagine counterfactuals. But it’s an interesting thought experiment.

Senator McCain criticized the stimulus bill as “generational theft,” and he eventually voted against it. He also proposed an alternate stimulus bill that was about half the size of the one eventually passed and that relied more on tax cuts.

Given all this, it seems the economic situation would look very different than it does today, for better or for worse.

But would it really? The dirty little secret that many people don’t realize is that monetary policy, not fiscal policy, has been much more aggressive in addressing the current crisis.

In fact, trillions of dollars more aggressive.

As of mid-May, less than 5 percent of the $787 billion available in stimulus funds had been spent. For comparison’s sake, take a look at this graph showing the expansion of the Fed’s balance sheet, which Joseph Brusuelas at Moody’s Economy.com refers to as the “magma chart.”

Most people don’t realize how much more active monetary policy has been for two reasons:

The Fed doesn’t have to seek congressional approval to kickstart most of the programs it’s enacted since the start of the crisis, so there’s no long, drawn-out, media-smothered lead-up to the expansion of the Fed balance sheet. The Fed just does what it does, with little fanfare and few talking-head blowhards debating it on T.V. Monetary policy is complicated, and many of the Fed’s programs are very difficult to understand. It’s much easier to understand (and frankly, for journalists to write about) a program to spend money to build a new bridge than a program called the “Asset-Backed Commercial Paper Money Market Mutual Fund Liquidity Facility.”

Monetary policy is by and large set by the Fed, which is set up to be an independent organization. Many economists I’ve spoken with in recent weeks have referred to Ben S. Bernanke, the Fed chariman, as an “unsung hero” of the recession, and credited the Fed with doing most of the heavy-lifting in stabilizing the economy.

So if, compared to stimulus spending, the Fed’s programs are A) more aggressive, B) more effective and C) likely to have remained the same under a different administration, then the implication is that we’d probably be in the economic place we are now even if Mr. McCain was president.

I called Tyler Cowen, an economics professor at George Mason University and super-blogger at Marginal Revolution, to ask his thoughts about this alternate universe question. He said that, by coincidence, he and his colleagues had been arguing about the exact same premise over lunch today, and the conclusion was that things would probably look about the same.

The one surviving counterargument, he said, was that President Obama has done more to bolster confidence than John McCain might have, whether because of President Obama’s looks, smooth-talking or what have you.

“That’s plausible,” Professor Cowen said, “but it’s hard to know how big that effect would be.”

Of course, having a different president could have set off a whole other set of unknowable ripple effects in international relations or other types of policies that affect the economy (butterfly effect and all that). Still, I’m curious to hear what readers make of the general argument.