http://running2016.com/html/canadian_ted.html
Was Cruz’s mother a citizen? Seems to be questions about her citizenship.
There are no reasonable questions regarding her citizenship. US Citizenship cannot be lost by accident or neglect. The only way she could have lost her citizenship is by an affirmative act of revoking it.
Such an affirmative act would be in a record of it at the State Department. If any such record of renouncement existed, Trump's opposition research team would have found it.
Ergo we can conclude there are no reasonable questions regarding the citizenship of Ted Cruz's mother. All such efforts to call it into question are the product of an intent to deceive people, and they should be denounced vigorously as a lie.