Republican presidential candidates Donald Trump and Ted Cruz are about neck and neck atop the GOP presidential field, according to a new NBC/WSJ national poll. It marks the first national poll without Trump leading since late December and the first time he is not numerically ahead since Nov. 9. It's also Trump's lowest support in a national poll since late November. This poll was taken entirely after Saturday's debate, where Donald Trump took repeated swings at former President George W. Bush...