I sure don't think of the northeast that way. I see it as fairly conservative both in politics and business. One data point is that it wasn't anywhere in the northeast that first legalized weed. It was Colorado and Washington, followed by Oregon and Alaska. Another data point is that people wear jeans or shorts at work in Silicon Valley (or Socal, Oregon, Colorado, etc) whereas they're far more likely to be required to wear suits in the north east.
The northeast is very urban, which has some overlapping effects with but is still very different from actually being liberal. Change is mostly driven by the west. It's just that the change reaches the dense cities of the northeast more quickly than the rural areas in between.
But agreed, there's absolutely a huge difference between west coast liberals and east coast "liberals".
The marijuana issue is an interesting thing to look at too, when you compare to red-vs-blue state maps. The "liberal" northeast still hasn't legalized weed (not even Vermont), whereas Colorado was one of the first two, and CO is a rather purple state (CO Springs is a ridiculously conservative place), and Alaska is very much a red state, being the place that elected Palin governor. It really seems to come down to social libertarianism versus authoritarianism. The "liberals" in the northeast want to ban sodas for your health, whereas the liberals in the west want to legalize drugs.
Because the Northeast was also the most heavily developed area of the country before the Interstate Highway System came about with a funding system that made non-toll roads the norm for new limited-access highways (funding rules which have since changed, weakening the financial incentive against new toll roads.) Modern political orientation has little to do with it: outside the Northeast, the people trying to introduce toll roads where they haven't been in the past are conservatives, the people opposing them are liberals.
Then, when you realize that toll roads are correlated with population density, perhaps you could realize that toll roads are then only also correlated with politics of state, not caused by them.
For example: If liberals loved toll roads, then California, Oregon and Washington would be full of them. But only the NorthEast is, right?
So your hypothesis falls apart here anyway.
BTW, the population density of metro areas in California is higher than most places in the northeast.
I just want to make one glib comment here about liberals and regressive taxes.
The Northeast is generally thought of as the most liberal part of America (aside from coastal California maybe). So why is it that I've seen far more toll roads and bridges there than in any "red state"?
I think some liberals make some good points about regressive taxes, but in practice, it seems like the liberals who actually get to power just love them.