Just for my clarification, When did Senator Cruz give up his Canadian citizenship, and when was the senatorial election?
Has Trump given up his British citizenship, given his mother was Scottish, thereby making him eligible?
Of course not. Because we don’t care what stupid citizenship laws are in other countries.
All the birther stuff is stupid.
Taking you seriously...
Legally, Cruz never had Canadian citizenship. He was eligible for Canadian citizenship, but would've had to formally opt for it once he reached his majority. As you doubtlessly know, Cruz formally rejected any claim to Canadian citizenship last August. Legally, he didn't need to do this as it had no effect on his status as an American citizen-at-birth -- fully eligible to serve as president.
Cruz was elected to the Senate in 2012.