Michael Barone breaks down the polls:

“Let’s take a look at the polls for the two parties’ nominations and for the general election as of mid-March, based on the compilations in realclearpolitics.com.

First, the Republicans. I’ve calculated the average percentages for Rudy Giuliani, John McCain, Mitt Romney, and Newt Gingrich for each month and for each have indicated the number of polls represented.

Polls Giuliani McCain Romney Gingrich Others, undecided
March 2007 7 37 21 8 11 23
February 2007 13 35 20 8 11 26
January 2007 9 29 23 7 12 29
December 2006 6 30 25.5 6 10 28.5
November 2006 5 27 27 7 7 32

Conclusions: This confirms Giuliani’s significant rise from the 27-to-30 percent level of November to January to the 35-to-37 percent level of February to March. Also, McCain’s fall from 25.5 to 27 percent in November to December to 20 to 23 percent in January to March. Also, note that the percentages for others and undecideds have been declining, roughly in tandem with the move to Giuliani; Romney’s numbers have not had a significant change, and neither, it seems, have those of Gingrich, who in any case is not a declared candidate. Yes, there’s a market out there for another alternative. But it’s not a market that has been expanding.”