BOSTON (AP) -- As Massachusetts governor in 2005, Republican Mitt Romney crafted a death penalty proposal so tightly drawn it virtually guaranteed that only the guilty could be executed.

But his biggest challenge was getting it through an overwhelmingly Democratic Legislature.

Romney -- now the Republican candidate for president -- ultimately failed. But he claimed success in creating what he called a "gold standard for the death penalty in the modern scientific age."

The proposal limited capital punishment to a narrow spectrum of crimes and included layers of safeguards, such as requiring that physical evidence directly link the defendant to the crime.

Some conservatives say Romney's plan would have made it virtually impossible to execute anyone.

Romney's campaign says he supports the death penalty and worked hard to make it legal in Massachusetts.