What's the best evidence that things are really changing in the Mideast? It is the spectacle of Israel and Saudi Arabia, hitherto America's two closest allies in the region, glowering darkly on the sidelines (and more or less in unison) as the United States and Iran begin an engagement that is already more profound than anything we've seen since the Iranian revolution of 1979. This historic shift, punctuated by the signing Saturday of a six-month, nuclear-freeze deal that both Israel and Saudi Arabia had loudly opposed, could potentially transform the entire region.