At this point, a wide range of economists agree that any plan to avert a breakup of the euro zone will have to involve the European Central Bank stepping up and pledging to backstop the debt of countries like Italy and Spain. Those calls have only grown louder this week, as the bond market went haywire and the contagion spread to once-safe countries like France.

Will the ECB bail out Barcelona? (Emilio Morenatti/AP)

Not really, say experts. It’s true that the Treaty of Lisbon expressly forbids the European Central Bank from buying up debt instruments directly from countries like Italy and Spain. But, says Richard Portes of the London Business School, there’s nothing to prevent the central bank from buying up Italian and Spanish bonds on the secondary market from other investors.

“If that’s illegal, then officials should already be in jail,” says Portes. “Because they’ve been doing it sporadically since May of 2010.” The problem is that the bank’s current erratic purchases only seem to be creating more uncertainty in the market. “Right now,” says Portes, “nobody’s buying in that market except the ECB.”

Instead, what many experts want the European Central Bank to do is to pledge, loudly and clearly, that it will buy up bonds on the secondary market until, say, Italy’s borrowing costs come down to manageable levels. In theory, says Portes, the central bank wouldn’t even have to make many purchases after that, because expectations would shift and become self-fulfilling. In the near term, investors would stop worrying about whether they’d be repaid for loaning money to countries like Italy, and Italy’s borrowing costs would drop — giving it room to figure out its debt woes. (Granted, that latter step is a daunting task.)

There don’t seem to be any legal strictures preventing the ECB from doing that. “It’s perfectly within their mandate to maintain financial stability,” adds Daniel Gros of the Centre for European Policy Studies. Instead, says Gros, “the main reservations are political.” Many German officials see any pledge to buy up Italian debt as a straight-up wealth transfer to their irresponsible neighbors down south. What’s more, if the ECB did calm down the markets, it would ease the pressure on troubled countries to carry out economic reforms. In essence, as Jacob Funk Kirkegaard told me recently, the ECB is engaged in a “game of chicken.”

But it’s a dangerous game to play. “The only option left is the ECB,” says Portes. He notes that the central bank will probably need political backing before it can move to calm the markets and haul financially strapped countries out of the danger zone. “The bottom line is that [German Chancellor Angela] Merkel and [French President Nicolas] Sarkozy need to agree to this approach, particularly Merkel. They’re the ones who need to realize that this is the only way they can save the monetary union.”