Julian Zelizer: Partisanship has taken its toll on Washington. While this is not the first period in American politics where partisan polarization divided the nation—think of the late 19th century, for instance—this is one of the worse periods. There is just very little common ground on Capitol Hill. I agree that Trump is a product and not a cause of bitter polarization. As the gridlocked nomination of Merrick Garland reminds us, politics was pretty bad before Trump took center stage.
I don't think there are many straws in the wind though. Partisanship is not a product of bad feelings or had people but of institutions and political structures, as well as demographic changes, that push our leaders apart. All of those remain firmly in place.
The only way we really make progress is to reform the way that politics works. Without changes to our districting process the Freedom Caucus will remain in place. Without campaign finance changes politicians will still be turning to issue based interest groups who will pressure politicians to stick to the party line. We would also need changes in non-government institutions such as media outlets to obtain less partisan news. Those changes can't be legislated but will have to be a product of the producers and editors who make the news.
Until the nation does the partisan pressures will only intensify and it's hard to see the light that would move the leaders of the parties to change directions. Trump might certainly be an outlier in his behavior and more uncontrollable than anyone else in the White House but he reflects the way partisan polarization has reshaped the fundamentals. Perhaps the reason that the Gorsuch nomination process was so hard to watch was because it simply exposed our current state of politics.
Keller: I don't fully agree. While political events like the 2000 and 2016 elections exacerbated the gridlock of the political process, the fact remains that politicians tend not to be so much ideologues as rent-seekers who, yes, do what they believe in but are also, when it suits them, able to function across party lines and get things done. (Take, for example, Clinton's reset on Serbia-Kosovo in the 1990s, his welfare bill, or Bush and Kennedy and No Child Left Behind.)
You are quite right to emphasize the current intensity of political polarization. But that has happened before: e.g., the slavery-secession division of the 1850s (a discouraging example), and the anti-FDR/anti-New Deal furor of the mid-1930s (a more hopeful example). The ferocity of the anti-Roosevelt rhetoric easily matches that currently directed at Trump.
If Trump should adopt a more tempered approach to his presidency (increasingly a political necessity, though there's no telling with him), there won't be an explosion of political good feeling. But there may be a chance of something closer to the customary American political ambience of highly contentious but mutually beneficial wheeling and dealing.