Editor's note. Please let me know what you think at daveandrusko@hotmail.com.

Although it's true you can almost never say never, when former Republican Tennessee Senator Fred Thompson officially announced last week that he is a candidate for the Presidency, it likely completed the field. What can we say at this juncture, 14 months from the next presidential election and four months out from the first primaries and caucuses?

At the most obvious level, all the Democratic candidates--the heavy hitters like Clinton, Obama, and Edwards, and the second and third-tier candidates alike--are pro-abortion. All the Republicans-- with the conspicuous exception of former New York City Mayor Rudy Giuliani--are pro-life.

So how in a party that is predominately pro-life can Giuliani be ahead in the opinion polls? If we believe the major media (which are heavily invested in breaking up the coalition that has won the presidency with pro-life nominees six of the past eight elections), it's because people no longer care about the abortion issue. Let's examine why this is not true.

Giuliani benefits from being the favorite son of pro-abortion Republicans. This truism--that there are pro-abortion Republicans just as there are pro-life Democrats--is virtually never mentioned, nor how important this core group of supporters is to Giuliani spelled out.

But the implications of the other obvious factor are either overlooked or not thought through carefully. And that is that in spite of the hyper-advanced pace of the 2008 presidential campaign, a lot of people are not familiar with all the candidates, a point made thoughtfully in a column last week written by Peter A. Brown, the assistant director of the Quinnipiac University Polling Institute.

Referring to the Gallup Poll's Lydia Saad, Brown writes that Saad "makes a strong argument based on the polling data that Giuliani's lead is built strongly on greater name recognition among Republican voters and is likely much less solid than Clinton's among Democrats."

To directly quote Saad herself, "The implication is that Giuliani is at greater risk than Clinton in losing support as the campaign progresses and his opponents become better known."

One easy way to gauge this is to compare Giuliani's support among the 54% of Republican voters who say they are not familiar with the broader field of candidates with the 46% who are familiar with all four leading GOP candidates -- Rudy Giuliani, Sen. John McCain, former Massachusetts Governor Mitt Romney, and former Senator Fred Thompson.

Among the 54% who are unfamiliar with the broader field of candidates, "Giuliani leads with 38% of the vote, compared with 18% for McCain, 12% for Thompson, and only 6% for Romney," according to Saad.

But among the 46% "of Republicans who are familiar with all four candidates," Saad writes, "the leader is Thompson with 33%. Giuliani ranks second with 25%, followed by Romney and then McCain."

This "suggests the possibility for a significant shift in Republican voter preferences as the campaign continues," she concludes.

So what can we know? That (a) pro-abortion Giuliani's lead in public opinion polls is based on incomplete knowledge--and not just among Republicans; and that (b) pro-life Thompson's official entry will change the dynamic of the Republican contest.

If you have any comments, please write Dave Andrusko at daveandrusko@hotmail.com.