New Iowa Poll Shows Ted Cruz and Donald Trump in Tight Battle

— -- Republican presidential candidates Donald Trump and Ted Cruz are locked in a tight battle for the lead in Iowa, according to a new Quinnipiac University poll released today.

Just three weeks from the crucial, first-in-the-nation contest, real estate mogul Donald Trump earns 31 percent support in the poll. Texas Sen. Ted Cruz has 29 percent support -- within the poll's margin of error. Third place belongs to Florida Sen. Marco Rubio with 15 percent. Ben Carson has tumbled from his previous lead down to only 7 percent. These numbers are similar to the Quinnipiac poll results released in mid-December.

Chris Christie has 4 percent support in the new poll, while Jeb Bush and Mike Huckabee garner 3 percent. John Kasich and Rand Paul have 2 percent, while Rick Santorum and Carly Fiorina have 1 percent.

Cruz's strong standing in Iowa is largely thanks to support from tea party backers and evangelical Christians. Still, likely GOP caucus-goers choose Trump as the best candidate on the economy, terrorism and illegal immigration. Trump also earns more support from men and from voters without a college degree.

Cruz and Trump have been sparring with each other over the last week, as Trump raises questions about whether Cruz is a "natural born citizen" and eligible to be president. Cruz was born in Canada to an American mother and Cuban father. Most experts say he is eligible to hold the office, but it has never been decided by the Supreme Court.

Trump leads national polls by a wide margin. He also leads in New Hampshire by double digits over a splintered field of establishment candidates. Still, Cruz has recently been a favorite to win the Hawkeye State, thanks to support among tea party backers and evangelical Christians.