"Why do affluent, white-collar, highly educated citizens in these cities tend to be liberal and vote Democratic?"
That's an easy one. They are extremists clinging bitterly to their atheism, abortions and amnesty.
Being unable to control the impetuosity of my thoughts, I found that this comment was too long to post on "that other site".
Let us not mythologize about the former nature of cities. Not so long ago antique shops were filled with pocket pistols and sword canes, the sword canes were not because our ancestors were feeble. Armories were located in the best neighborhoods, to offer sanctuary when "the rabble rose in the streets".
The “Curley Effect”. For those not familiar, Curley was one of the most corrupt mayors Boston has ever had. He was even re-elected in jail. Those who read the Boston papers will understand that he has not lost his charm. About 10 years ago there was a great search conducted to find "Curley's Desk", so that it could be returned to the Mayor's office. Real estate developers remember him best for his establishment of neighborhood clinics. To accomplish this he approached Boston's real estate king pin (I believe the name was White, but I am probably mistaken). He explained to Mr. White that he needed to build neighborhood clinics and would probably have to raise taxes. Since Mr. White was Boston's largest taxpayer, it was understood who would be hurt the most. At Curley's advice, Mr. White agreed to "donate" the funds required. This is now official policy in Boston, and many cities; it is now known as "linkage".
Some asides. Some years ago I was involved with renovating a few buildings in Boston's South End. The "Brownstones" were acquired by young couples. As soon as their children reached an age to go outside, they built 10 foot masonry walls around the "rear yard". When the children reached "school age", they moved. The politicians view "urban pioneers" solely as "taxpayers", they are unmoved by their concerns. A friend offered to sponsor a benefit party for a City Councilor at his Back Bay home. He was told to just send the money the party would cost, the people likely to attend "didn't vote anyway". The same is probably true in Providence. I suspect many on College Hill are transients. The entire East Side is probably not home to more than 15% of the voters. When I moved back this way about 17 years ago, I was astounded at tax bills on the East Side, relative to value. I suppose someone had to support the city. As neighborhoods grow poorer, the tax assessments go down.
Another factor often overlooked is "shrinkage". Providence's population is only about 60% of what it was in 1950. There should be surplus housing aplenty.
Taxing based on the value of a home seems silly. It's regressive in many circumstances, arbitrary in others, and subject to all sorts of political shenanigans. Worst of all, when the tax rate is high, it actually encourages people to devalue their homes and forgo things like additions.
We should be taxing income, if anything, then reimbursing the towns and cities based on where the income was generated and who generated it (so I made $100 at work in Providence, I live in Pawtucket, and I paid $3 in state income taxes on it. Give $1 to the state, $1 to Providence, and $1 to Pawtucket, or something like that). If local taxes need to exist, then we should be taxing 'square footage' instead of 'value', which would encourage high value, high density growth.