The report and the press release.  From the executive summary:

While RNLA agrees with a majority of PCEA’s recommendations, we caution against the Commission’s recommendation that states embrace expanded early voting as a solution to the systemic election administration problems identified in its report. The experience from recent elections demonstrates that early voting does not solve the problem of long lines. It is also expensive, distracts from Election Day preparations, and diminishes the importance of Election Day. Most Americans continue to prefer to vote alongside their neighbors and fellow citizens at the polls on Election Day so reform needs to start there. Accordingly, states should instead invest their limited time and resources fixing the problems at the polling place and ensuring a smoother absentee voting process for those who use it out of necessity, not convenience.

Here’s my view on the conservative resistance to early voting.