"A slow-moving train wreck." That's what Daniel McNamara, the founder of Polpo Capital, calls the upcoming wall of maturities — the massive amount of commercial mortgage-backed securities coming due in the next year or two. Many, especially those who used floating-rate debt are facing a triple threat: the triple whammy of higher interest rates, lower valuations and more conservative lending. All of that is making it difficult for commercial landlords to refinance and leaving CMBS investors at risk.