He predicted Trump had a 29% chance of winning? I didn't know that.

He wasn't the only one--and if you recall (and it may have been brought up in the article, haven't read it yet) there were a lot of questions after the election about the inadequacy of polling. Those questions still remain, and have nothing to do with Trump. What's also been proposed, specifically to do with Trump, is that people were hesitant to say they were going to vote for him, or decided at the last minute, and thus their preferences (or lack of same) were never registered in the polls.

And they are still calling people on land lines.

Some stats on landlines. Changing rapidly of course, but as of the end of 2016, there were still quite a few houses with landlines, close to half:

https://www.cdc.gov/nchs/data/...e/wireless201705.pdf

Gallup on the cell phone issue: https://news.gallup.com/poll/1...all-cell-phones.aspx

We only ported our home/landline phone number to a mobile phone last year. I can't tell you how many people I know who still have landlines and who still use their "home phone" for calling and only use the cells when they are away from home. Certainly a dying breed, but by no means gone.

The other thing I wonder about is the portability of phone numbers. Phone numbers used to be tied to location, and they're not anymore. From what Gallup wrote above, apparently there is some way they can tell if a number is a cell or a landline. What about people who got their number when they lived in California, but now they've moved to Georgia?

There are a lot of other issues than age/ethnicity when dealing with cell phones v landlines. Probably the most important is caller ID and screening. Many landlines charge extra for caller ID, most cell phones do not. Many younger people screen all calls. Older people tend not to, and also have landlines.

I totally trust Gallup's ability to create and analyze a statistically meaningful sample. They have some of the best statisticians in the business. But it's not at all clear to me how well some of the other polling groups correct for cell phone use.

To your other question, you can definitely port your cell phone number wherever you go. My cell phone still has an AZ area code. I don't know how they figure out that I'm not in AZ. Maybe they don't, maybe they do. I have no idea. I also know someone who specifically requested a Green Bay area code on their cell phone (Packers fan), even though they lived thousands of miles from Wisconsin.