This is the tale of two polls.
The first was done by Mason-Dixon, between August 8 and 11. It surveyed 400 likely Democratic primary voters with a margin of error of 5 percent. It found Kendrick Meek had a commanding lead over his Democratic Senate primary opponent Jeff Greene. Meek got 40 percent. Greene got 26 percent. That’s a 14 point advantage for Meek.
The second was done by Ipsos, between August 6 and 10. It surveyed 237 registered Democrats (not likely voters), with a margin of error of 6.4 percent. It found that Greene had a commanding lead over Meek. Greene got 40 percent. Meek got 32 percent. That’s a 8 percent advantage for Greene.
In summary: Two polls at basically the same time find results that vary by a spread of 22 percentage points. So much for the margin of error.
The most obvious explanation for the different results is the Mason Dixon definition of likely voters. The motivated base of the Democratic party, it seems, is more interested in voting for Meek, who is the choice of President Obama and basically the rest of the national establishment.
But the two polls can also serve as a cautionary tale: All polls may not be created equal. The Miami Herald, The St. Petersburg Times, BayNews9 and Central Florida News 13 paid for the Ipsos poll, which, if the Mason Dixon poll is right, may not have much value to readers. By the same token, if Mason Dixon has misjudged voter turnout, then the local news organizations could be vindicated.
The good news is that polling on elections can eventually be checked against a real-word result. Sooner or later, we find out who was right all along. Primary day in Florida is August 24.