New Jersey guy Christie has double-edged appeal

It seems a natural assignment for Chris Christie, the bombastic, in-your-face New Jersey guy whose confrontational style as the Republican governor of a liberal state has made him a rising political star.

Christie, who gives the keynote speech at the Republican convention on Tuesday, may not be used to being an opening act but he is perfectly comfortable delivering the red-meat rhetoric that fires up conservative activists.

And when he lays out Republican presidential contender Mitt Romney's case for a change in leadership from President Barack Obama, he will take a big step into the national spotlight with implications for his own potential White House bid in 2016 or 2020.