It's not whether they will or won't cut rates at the end of their two-day policy meeting on Wednesday, but whether Federal Reserve policymakers will call it a wrap in terms of the amount of stimulus they have introduced into the U.S. economy so far this year. 

Wall Street is fairly certain that Fed officials will lower rates by a quarter point, mirroring a similar pattern followed in the late 1990s by then Fed Chairman Alan Greenspan, who led the Fed in a rate about-face amid global economic and financial market turbulence that at that time was also threatening a relatively sanguine U.S. economy.

The question this time around is whether they can pull off a second third time's a charm - and whether another quarter-point cut is too much, too little, or just right to keep the longest economic expansion in U.S. history going.