The S&P 500 is awfully close to a key level: 2,800.

But just because it's close, doesn't mean it's going to breach it anytime soon, according to David Keller, President of Sierra Alpha Research.

Though if the broad index crossed that level, it would be a very bullish sign and pave the way for a retest of the January highs of 2,873, Keller said. 

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