Believe it or not, the U.S. stock market could get too hot.
If the bull market gets ahead of the economy, fears of a bubble in equities or sexy sectors like biotech will reemerge.
The stock market doesn't appear to be near that point yet. While the Nasdaq has climbed 10% this year, the S&P 500 is up just 3% and the Dow barely 2%. That's hardly overheating territory.
But it's a risk worth keeping an eye on given that stocks are expensive by historical standards.
"Valuations are stretched. We're moving into overvalued territory but not extensively into that area yet," said McCain.
Related: Find stocks expensive? Bonds are pricier
