I doubt there’s any actual issue with the fact that Ted Cruz was born in Alberta, since his mom was a US citizen, but I’m not surprised he’s getting birfered:
The poll finds that the ‘birther issue’ has the potential to really hurt Ted Cruz. Only 32% of Iowa Republicans think someone born in another country should be allowed to serve as President, to 47% who think such a person shouldn’t be allowed to serve as President. Among that segment of the Republican electorate who don’t think someone foreign born should be able to be President, Trump is crushing Cruz 40/14.
When it comes to the GOP these days, I follow the rule of Murdoch’s Razor: the stupidest explanation is usually correct.