Investors are looking to the European Central Bank to live up to a rather lofty advance billing as it attempts to beat back deflation and resurrect the region's economy.
"Markets have been waiting 2 1/2 years for ECB President Mario Draghi to put pen to paper on his promise that he'd do whatever it takes, so the larger risk is for Draghi to do something less than spectacular," Art Hogan, chief market strategist at Wunderlich Securities, said.
Reports published Wednesday signaled that the ECB would unveil a bond-purchase program of at least 500 billion euros and possibly closer to 600 billion euros, pushing U.S. equities higher and elevating the risk of investors getting a less-than positive surprise.
"I'd be surprised if it's a number that is considerably less. If it's close, and Draghi effectively delegates the purchase program to the various sovereign banks, I don't think it will be a surprise, or a big market mover," Hugh Johnson, chairman of Hugh Johnson Advisors, said.
"This is their moment in the sun, so to speak," Johnson added.