I can highly recommend this report from E3 analyzing 4 approaches to reduce GHG emissions in the PJM service area. E3's findings concur with my own research on a Clean Energy Standard (CES), as opposed to carbon pricing to reduce GHG emissions;
Key Finding #2: A regionwide, technology-neutral Clean Energy Standard (CES) approaches the efficiency of a direct carbon policy in achieving low-cost emissions reductions in the power sector.
A CES is more conducive to state policy drivers than carbon pricing.
The key benefits of the CES is its ability to harness technological and geographic diversity to drive the least-cost outcomes for electricity customers.
CES policies do not directly target carbon emissions; rather, they create incentives or mandates for the market to favor lower-emitting alternatives. CES policies that maximize choice for the marketplace lead to lower-cost outcomes
Other key findings are that a region-wide Clean Energy Standard can approach the efficiency of a carbon pricing system, that applying carbon pricing to only part of the PJM footprint could result in both higher costs and higher carbon emissions, and that 50-90 GW of firm capacity continue to be needed through 2050 even under 100% GHG reduction scenarios.
I highly commend the authors for their objective, honest and proficient analysis.
The "Always on Capacity Exchange" is one such wholesale market based CES solution that is worth considering.