The Washington Post reports:
The former House speaker launched a TV ad Thursday in New Hampshire and South Carolina, the first in which he challenges Romney.The ad uses the word "timid" three times. Even when you'd expect to see the noun form — "timidity" — the ad still uses the adjective "timid" as if it were a noun. So, Gingrich clearly decided that "timid" is a word that could stick to Mitt Romney.
“Romney’s economic plan? Timid,” the spot says. “Parts of it virtually identical to Obama’s failed policy. Timid won’t create jobs and timid certainly won’t defeat Barack Obama.
The ad highlights Gingrich’s “bold leadership” and says: “The Gingrich jobs plan: A powerful plan for growing our economy and creating new jobs.”
It seems like the creators of the ad decided to play around with the name "Mitt," so they flipped it over to get "tiM," flopped it back so it's "Mitt" again, then put them side by side to get "tiM-Mitt," which sounds like "timid."
Aside from whatever substance their might be to Gingrich's disagreements with Romney's economic policy, the undertone to this ad is that we're supposed to view Romney as too cautious, too restrained, too afraid to do the kinds of huge things Gingrich likes to do. Whether that will convince voters that Romney is the less conservative candidate, I'm not sure.
Personally (though I can't claim to be representative of voters in the Republican primaries), I like the idea of a candidate who's cautious and sensible, not prone to making rash decisions. I might even care about this more than any conventional distinction of left vs. right.