Pollsters say that the Presidential election is tight.
The same pollsters say that the race for the House is over, with Republicans hanging on to a substantial majority.
I posit that they can't both be right. In 2008 Obama won the Presidency by a margin of 6.8%, while Congressional Democrats won by a cumulative total of 10.4%. In 2004 Bush won the Presidency by a margin of 1.5%. Congressional Republicans won by a cumulative total of 2.6%. What that suggests to me is that the House vote and the Presidential vote are correlated, with the party winning the Presidency also winning the House, and generating slightly more votes for the House than the President. Meanwhile, in 2010 Republicans won the House by a cumulative margin of 6.8%.
If Republicans are going to win the House easily, as the RCP map suggests, I don't see how Romney doesn't win the Presidency.