Signs of Imminent Demise for Gingrich?

A couple of things are hitting the news today that could concern the Gingrich campaign.  First, he appears to be slipping in Iowa, just a few weeks before the caucus.  Secondly, in a recent NBC News/Wall Street Journal poll, Gingrich did not poll well against the President, not only seeing a 51-40 percent deficit against Barack Obama, but also having 50 percent of participants saying that they absolutely would not vote for the former Speaker of the House.  Is this just a poll that will change in time or is this a serious concern for Newt and his campaign?