Now that Newt Gingrich has become the latest in a series of Republican front-runners, he is getting the kinds of scrutiny and attacks that have done in other front-runners.

The United States is a country that has been peopled largely by vast surges of migration -- from the British Isles in the 18th century, from Ireland and Germany in the 19th century, from Eastern and Southern Europe in the early 20th century, and from Latin America and Asia in the last three decades.