Thompson released his ad ahead of it’s scheduled showing tonight during the debate:

Fred Thompson’s image will begin appearing on the small screen today, not as District Attorney Arthur Branch, but as an official candidate for president.
In a 30-second campaign commercial sent to networks for broadcast at midnight, Thompson warns that “On the next President’s watch, our country will make decisions that will affect our lives and our families far into the future. We can’t allow ourselves to become a weaker, less prosperous and more divided nation.”
Thompson concludes the ad with an invitation to visit his new campaign website, Fred08.com, on Thursday to watch a 15-minute video in which he officially announces his campaign for the White House. But if there is any doubt, an announcer then comes on, saying: “Fred Thompson, Republican for President.”
The ad will air throughout the day today and during the New Hampshire Republican presidential debate on Fox tonight. Following the debate — which Thompson is skipping — he will appear on Jay Leno’s “Tonight Show.”
The idea, advisers say, is to create a national buzz about Thompson’s official entry into the race and drive traffic to the new website on Thursday. The 15-minute video will be available on the website at 12:01 a.m. Thursday morning; advisers hope it steals the show the next morning on talk shows and cable news networks.
[…]
The script of the ad, titled “Debate”
FDT: I’m Fred Thompson and I approve this message. On the next President’s watch, our country will make decisions that will affect our lives and our families far into the future. We can’t allow ourselves to become a weaker, less prosperous and more divided nation. Today, as before, the fate of millions across the world depends on the unity and resolve of the American people. I talk about this tomorrow on Fred08.com, I invite you to take a look and join us.

Finally! It’s about time.