Today, someone at CNBC didn't:
Asset allocation strategists haven't had an easy time in recent years. They've grappled with deflation, recession, plummeting U.S. stock markets and surging
foreign economies. And for awhile they dished out bigger weightings to defensive plays-bonds, cash and commodities.
"Awhile" is an adverb. "While" is often a noun.
Prepositions like "for" take nouns or noun phrases as their objects -- not adverbs.
So after "for" you'd want the noun phrase "a while."
Here's how Webster's New World puts it:
Usage Note: Awhile, an adverb, is never preceded by a preposition such as for, but the two-word form a while may be preceded by a preposition. In writing, each of the following is acceptable: stay awhile; stay for a while; stay a while (but not stay for awhile).