One way I check this is to look at the mid-year execution numbers.  As of now, the country has executed 13 killers in 2017.  That would extrapolate to a total of 26 over the year, six more than last year.  If that's the way it holds, it will be one of the few times over the last two decades that we've had more executions in one year than in the preceding year. See this graph. 

I also look at Supreme Court cases to see who is voting which way.  Today, Justice Kennedy voted with Justice Thomas's majority opinion in Davilla v. Davis, noted briefly by Kent here.  He did so without writing separately from Thomas's strong and disciplined analysis, just as he cast his vote without separate opinion in the Court's extremely important work in Glossip v. Gross.  It seems to me that Justice Kennedy's once seemingly skeptical view of capital punishment (see Roper v. Simmons) is not what it used to be.  It may also be worth noting that, if Justice Kennedy steps away from the Court in the near future, his replacement is likely to be a solid death penalty backer, as is  --  to add to my main point  --  the Court's youngest member, Neil Gorsuch, whose votes continue to be everything capital punishment advocates could have hoped for.

Finally, as the sickness of a skyrocketing murder rate continues to afflict the country, now into its third year, support for the strongest antidote is correspondingly likely to rise. This too is what history tells us.  --  support for the death penalty rose massively until several years after a spiraling murder rate started to decline.