If the euro is saved, the much-maligned power of global financial markets will deserve much of the credit.

The conventional wisdom among many on the intellectual left is that unbridled financial players threaten to destroy the European Union, one of history’s noblest, war-ending projects. The truth, however, is something else. To be sure, speculators lack noble motives, and global capital is a blunt instrument that tends to overshoot. But markets are forcing European leaders to fix their fatally flawed monetary union, a union that can only last with deeper economic integration and greater political (and democratic) legitimacy.

Last weekend’s agreement by Spain to accept a bank bailout, based on a European aid package of $125 billion, is a dramatic case in point. Senior Obama administration officials, in a series of urgent conversations with their European counterparts, warned that Spain posed the possibility of a “Lehman moment,” with global reverberations that no one could predict. If European leaders didn’t demonstrate to markets that they would pool their resources to address the banking meltdown of Europe’s fourth-largest economy, the contagion could have spread, what remained of U.S. and global growth could have evaporated, and the European Union itself would have been endangered.

In retrospect, it may have been wiser to build Europe without a common currency, one senior Obama administration official told me, given all the historical and national differences. However, now that the euro is used by 17 countries and has become a global reserve currency, the euro zone can’t be dismantled without unacceptable European and global risk. Thus, U.S. officials had been urging European leaders to settle the Spanish bank crisis before the Greek election next Sunday, June 17, and the G-20 meeting June 18-19, to avoid convening on the brink of financial catastrophe.

In the end, however, it wasn’t President Obama who forced a Spain deal through his lobbying with the top three euro country leaders – Chancellor Angela Merkel, French President François Hollande and Italian President Mario Monti. (Side note: One does wonder whether British Prime Minister David Cameron isn’t beginning to feel left out). Instead, it was the unrelenting pressure of European and global creditors and investors, who were withdrawing in droves from Spain, unsure whether a German-led Europe would provide the financial bazooka required.