Rich Arndt read this article I linked to about the Ted Cruz "birther" issue and sent me this…
I think both the article (which is just fine for what it covers) and your own remarks are missing a bit of the boat on Cruz's eligibility to be president. While Cruz is quite likely eligible the G.O.P. has spent years screaming that Obama isn't or wasn't eligible under nearly the same circumstances — i.e., that of having a U.S. mother and a foreign father. The reason Trump is bringing it up now (and likely the only reason he's bringing it up) is because he has to — he's made such a huge stink about Obama not being eligible that to set silent on Cruz's eligibility may cause his own supporters to wonder why he's not bringing it up.
With Cruz's run the G.O.P. in general has to deal with a lurking controversy that they themselves set into motion eight years ago with their own idiotic rantings against Obama's eligibility. It isn't so much the actual legality over whether Cruz (or Obama) is eligible to be president of the United States, it's how to deal with the hypocrisy of why a black Democrat isn't considered eligible to steward the country by conservatives because his father wasn't an American yet a white Republican, under much (perhaps even exactly) the same circumstances, is. And even that doesn't address the claim certain G.O.P. members (including Trump) made that because Obama was allegedly born in Kenya (a falsehood, he was born in Hawaii) he was ineligible to stand as president while Cruz, who actually is foreign-born (born in Canada) is eligible for the office.
I dunno…it seems to me simpler than that. Trump's bringing it up because there are people out there who are on the fence as to whether to vote for him or Cruz. And having this issue dangling out there will probably cause some of those folks to say, "We'd better vote for Trump just in case it turns out later than Cruz isn't eligible." As sleazy political moves go, this one ain't bad.