[Swordmaker]

Let's see... what determines a voter to be a member of the set of "likely voters?" They voted in the LAST ELECTION. And exactly what was the last election? Why the Democrat Primaries, of course!

[EllaMinnow]

From the article:

The larger fluctuation Gallup found among likely voters probably reflects the ebb and flow of news stories about the Democratic primaries, which in turn can affect the relative number of Democrats or Republicans in the "likely voter" pool at any given point in time. During a period of intense coverage of Democratic primaries and caucuses, as occurred during the New Hampshire primary and more recently in anticipation of the Wisconsin primary, Democrats become especially interested in following the campaign -- a measure that boosts their chances of being included in the Gallup "likely voter" model.

This is an unusual situation. Republicans are disproportionately likely to be likely voters in most situations, which has historically given them an advantage on Election Day. It will be important to see if the Democrats maintain their current level of intense interest in the campaign, and thus a higher probability of voting, after the primary season is over and a nominee has been firmly determined.

Over the same period of time -- between the New Hampshire and Wisconsin primaries -- Bush's job approval rating has remained essentially stable, ranging between 49% and 52%. Thus, the changes in the horse-race figures would appear to reflect more the changing likelihood of Democrats turning out to vote than a fundamental change in the public's perceptions of Bush.