Speaking as someone on the moderate left: Susan Collins is a loss.
Moderates on the other side keep us sharp. They have real objections, will work together on issues that matter to voters, and provide a mirror through which you can judge yourself.
This is not the same as those on the far right there are fundamental, basic, human disagreements with.
Figures like Collins and Romney made the Democratic party stronger because you had to measure yourself against them, and realistic, sane objections.
Even in this incredible blue wave, she nearly survived.
We should also remember that lesson with our own moderates: our incoming senators from places like Kansas, Texas, and Mississippi are not going to vote like NY or WA liberals, nor should they.
Embracing the moderates is how you keep your party in power and your platform responsive to voters. Excluding them to run to the extremes is how you end up like the Republicans did.
Goodbye, Senator Collins. We didn't always agree but you were one of the good ones.