The federal government is just too damn big.
Yes, political party polarization is increasing. And that is a problem--if an issue worth fighting over (such as slavery, in an era when we also had high party polarization) arises.
But trying to forge a sensible center is a losing response. No, reduce the scope of the federal government in our lives and we won't feel compelled to elect partisan hardliners to defend our views in Congress.
Honestly, if another state wants to institute single-payer health care, raise the minimum wage to $20 per hour, or make the 1% "pay their fair share," my interest in that state's experiment in fiscal suicide will be academic.
I assume that if Texas wants to reduce corporate income taxes, that Massachusetts voters won't stage "die-ins" in protest.
And state and local governments will anger people--let's not pretend, as some on the right are prone to do, that these levels of government don't do things that offend us. They do. Although in the issue cited, there is hope this trend can be reversed. But at least those problems are localized and not a threat to national unity.
Right now, absent a move to restrict the federal government to issues truly national (and international) in nature and allow states to forge their own paths based on their own wishes without nationalizing bike path-level politics, partisan "deadlock" in Washington, D.C. that at least prevents the federal government from making fiscal policy worse (although in the long run, policies already locked in place will make things fiscally worse)--"gridlock"--looks like a successful defense rather than a failed offensive.
Given all the issues the federal government has its hand in--remember when saying "don't make a federal issue out of this" meant don't make it such a big deal?--we aren't going to forge a mythical "no labels" consensus on all those issues that just don't belong at the federal level. The best we can do is reduce the number of issues we fight over at the national level.
I will also say that a focus on internal divisions rather than one that reduces the scope of federal power will all too likely focus on just one portion of the potential threat, as the Diamond's examples show, rather than be a real (but futile) attempt to find a "sensible center."
The federal government is just too damn big.