It doesn’t seem like there is much these days that can unite Republicans and Democrats. However, one thing both parties have consistently agreed on is that nothing should threaten their grip on power.
The current electoral process is designed to serve the interests of the dominant two parties and their members. If there is a reform that threatens to upset the apple cart, it will encounter resistance from those who have the most to lose from a fairer, more equitable process.
This will include leaders and members in both parties.