As The Atlantic points out in a recent article:
It's not anti-transit or anti-rail driving the skepticism; it's anti-bad rail transit.
As has been noted here on multiple occasions in the past, heavily-subsidized streetcars are a waste of resources that serve as little more than expensive tourism attractions. Counting the Portland Streetcar, there are a whopping ten in the USA, with a few more in the planning stages, and for the most part, they ain't worth spit.
The most commonly cited problem with new streetcars—Matt Yglesias calls it the "original sin" —is that they tend to run in mixed traffic alongside cars. The resulting slow speeds, combined with the relatively short length of the lines (often just a mile or two), means many potential riders could sooner reach their destination by foot. Streetcar advocates say slow speeds are not only beside the point but part of the charm, which might be true, so long as riders don't have somewhere to be.
That certainly fits Portland's streetcar; it's faster to go by foot than by streetcar, and the line runs all of about three miles, impeding traffic the entire way (well, seven if you count the extension to the east side of the river). That's not "transit", no matter how hard you pull to stretch the definition of the term. Another drawback from a transit perspective is the scheduling - or lack thereof; to be effective transit components, they need to show up at least every twelve to fifteen minutes, and in most cases, they don't. Portland's much-touted streetcars, in fact, only manage to hit the minimum transit standards during mid-day, which means that they contribute nothing to the stated goal of reducing traffic congestion during peak hours; worse, they have the opposite effect: they increase traffic congestion at the very times they're supposed to be reducing it.