Do longer sentences reduce crime?

I find that Republican prosecutorial offices sentence defendants to longer incarceration spells as compared to their Democratic and Independent counterparts. This increase in incarceration length is driven by longer sentences for both violent and prop- erty offenses, and translates into a persistent increase in incarceration. These sentencing and incarceration enhancements do not lower crime at the county level, indicating that, in terms of public safety, the marginal return to the tough-on-crime stance may be close to zero.

That is from a new AEA paper by Ashna Arora.