Hillary Clinton’s “3 a.m." advertisement (released in March) was named the “Best TV Spot” of the 2008 election, chosen by a large margin in a poll of Campaigns & Elections’ Politics magazine subscribers (many of whom are political professionals). Here are the complete results for the question in the poll:

Which of the following political advertisements would you say was the “Best TV spot” of the 2008 election?   
Hillary Clinton – “3 A.M.”    31%
Barack Obama – “The Moment”    24%
John McCain – “Celebrity”    11%
Mike Huckabee – “Chuck Norris Approved”    9%
Bill Richardson – “Job Interviews”    7%
Mitt Romney – “Experience Matters”    3%
Republican National Committee – “Storm”    3%
Mike Gravel – “Throws a Rock in a Lake”    1%
Other    4%
Don’t Know    6%

Clinton's ad did get a lot of attention, and may have helped her win many primaries after it was released—as well as spawning a multitude of parodies on YouTube. Here is the original ad:

The Clinton campaign used a fairly conventional logo design. It was patriotic, using a simplified, stylized flag. The type is serifed and classy, but not very modern in feeling, and there is good contrast. It is the only logo I have seen that employs just the first name, but that is to differentiate her from her husband, the ex-president. It also may have served to make her more "personable." As The New York Times pointed out, the "l"s and the "i" could be the number 1.

Her logo reminds me a little of the 2004 Kerry-Edwards design, with a similar font used and a flag (although less stylish) also shown waving, against a blue background that is close to that of Clinton's. The Kerry-Edwards campaign added a slogan, “A Stronger America,” in an attempt to show that the Democratic candidates would be tougher against terrorism. 

The Clinton design is more effective, because it is stronger, simpler, and more unified, with the "y" in Hillary joined with the flag.