A look at the past three weeks of polling shows clear trends in the race for the GOP nomination but the meaning of those trends is less clear.

Rasmussen Reports combines nightly Presidential Tracking Poll results into full-week averages and support for Fred Thompson has declined in each of the past three weeks. He earned 28% for the week ending September 16 and then saw his numbers fall to 26% and 25% in subsequent weeks. Now, for the week ending October 7, his support is down to 22% and he trails Rudy Giuliani by a single percentage point. This marks the first time since Thompson formally entered the race that he has trailed Giuliani in a full week of polling by Rasmussen Reports (see weekly poll results).

For his part, Giuliani’s numbers have remained fairly stable. With the exception of one week in September, he has remained at the 22% or 23% level each week since the end of summer.

Some people will interpret the downward trend in Thompson’s numbers as the Fred Fizzle that many Washington pundits have been anticipating. In this view, Thompson’s early campaign stops have been less than thrilling and his downfall is inevitable.

Others will say this is nothing more than the fading of Thompson’s post-announcement bounce. In this view, Republican voters are dissatisfied with the rest of the field and just getting to know the man from Tennessee.

It’s too early to tell which of these views is correct. When we average the results released by month, both Thompson and Giuliani have stayed between 22% and 25% each month since June. Thompson’s weakest month was August while Giuliani’s low point came in September. Both have remained well ahead of Mitt Romney and John McCain each month.

If Thompson’s numbers stabilize and he stays competitive with Giuliani, it will suggest that the last few weeks have represented the fading of his bounce. On the other hand, if his numbers continue to fall, it might mean that the pundits are right and his entire campaign is fading.

All in all, the new data does nothing to shake the basic assessment offered last week that the Republican race is getting murkier as time goes on. The continuing challenges faced by each of the leading Republicans may force the chattering class to wait for voters to get engaged before a clear frontrunner emerges. It is even possible, of course, that no clear frontrunner may emerge even after the dust settles following the nearly national primary day of February 5.

Rasmussen Reports conducts national telephone surveys on the Presidential race every night and releases updated data from our Presidential Tracking Poll by noon each day, Monday through Friday.

Those results are based upon a four-day rolling average and provide a quick update on the race.

In addition to the daily tracking poll, Rasmussen Reports provides weekly results to provide a longer-term overview of the race. These updates are based upon nightly telephone surveys. Results are reported based upon interviews conducted on the seven days up to and including the night before posting.

For the seven days ending October 7, 2007 show that Rudy Giuliani earns 23% of the vote while Fred Thompson attracts 22%. Mitt Romney has gained two percentage points and is supported by 15%. John McCain is now the favorite for just 10% and Mike Huckabee is at 6%. Four other candidates split 5% of the vote while 19% are undecided (review history of weekly results).

The seven day results typically include interviews with more than 1,000 Likely Republican Primary Voters. This includes both Republicans and those independents likely to vote in a Republicans Primary. In some state primaries, independent voters are allowed to participate in party primaries while in others they are excluded. The margin of sampling error for the weekly update is +/- 3 percentage points with a 95% level of confidence.

Updates prior to July 16 were based upon four days of polling conducted the Monday through Thursday preceding release.

Rasmussen Reports continuously updates general election match-ups and other key stats for all Republican and Democratic Presidential candidates.