I asked Scott Rasmussen what it means that Fred Thompson has lost a good chunk of ground in his firm’s daily tracking poll.

Rasmussen began by contending that the biggest difference between his company and other pollsters is that he and his team “are screening much more tightly – we’re getting people following the race much more closely.”

“Fred Thompson had a nice bounce after he announced, and for the past two weeks, that bounce has been sliding away,” Rasmussen said. “Is this just settling from the height of the bounce, or is this the ‘Fred fizzle’ that some had been predicting? I think in the next couple weeks, we’ll know the answer to that.”

Rasmussen noted, “Rudy Giuliani has been on top for a long time, and if you had asked me in January if he would be the frontrunner in October, I would have said no… I would note he’s still under thirty percent. Thirty percent does well when the rest of the vote is split among several other candidates. If it’s a straight up choice between Giuliani and Romney or Giuliani and Thompson, I’m not sure how that plays out. I’m not sure Rudy’s support can grow much, but it seems safe to say that those supporting him now won’t leave him.”#more#

Rasmussen noted three other trends since Fred Thompson’s announcement: “The percentage of Republicans who think he’s conservative has gone up a little. The percentage of the population who think he’s conservative has gone up a lot. And his general election matchup numbers have gotten a little weaker. He’s now seen as a more conservative and as a Republican instead of as the lesser-known figure he was before.”

I also asked about Ron Paul’s surprising fundraising numbers, and whether there’s some significant number of Paul-backers (Paulbearers?) who haven’t yet shown up in these polls.

“I do believe he has intense, passionate supporters,” Rasmussen said with a chuckle. “We get calls every day demanding to know why our polls don’t match the online polls showing Ron Paul way ahead. But fans of third party candidates always respond that way as well. During the 2006 cycle, in one of the Senate races we were polling, we didn’t include a candidate of the Green Party. We got copy of letter to a candidate from one supporter recommending she sue us.”

“We all hang out with people similar to us in some demographic or psychographic way – people who agree with us. From that, you assume there’s a bigger universe of similar-minded people out there. What the Internet has done is it lets a lot of similar-minded people find each other, and you can raise serious money that way.”