Donald J. Trump continued to fan the flames of doubt over Senator Ted Cruz's citizenship on Wednesday, suggesting that his Canadian roots might be a problem if he won the Republican presidential nomination. The decision to confront Mr. Cruz more directly comes as Mr. Trump, who has dominated most national and state polls for months, faces the prospect of losing to the Texas senator in next month's Iowa caucuses. Popular among evangelical Christians and conservatives, Mr. Cruz has become a favorite to win the first contest of the nominating process.
