Ted Cruz lawsuit challenges his eligibility for the presidency

A lawyer in Ted Cruz's hometown of Houston has filed a federal lawsuit challenging the Canadian-born senator's eligibility to be president.

In a complaint on Thursday, Newton Schwartz asked the US Supreme Court to decide if Mr Cruz's birth to an American mother and Cuban father while they lived in Calgary violates the constitution's "natural born citizen" requirement.

Mr Cruz argues that because his mother is American, he became a US citizen at birth. But the Supreme Court hasn't previously considered the eligibility question.

Presidential rival Donald Trump has repeatedly questioned Mr Cruz's presidential eligibility.

When Mr Trump again raised the issue in the latest debate on Thursday night, Mr Cruz said that though the constitution hasn't changed recently, his polling numbers have.