Are Campaign Slogans Getting Shorter?

In 2008, Americans elected a president whose slogan was the shortest ever, both in terms of syllables and length:  "Hope."  I wonder:  have US presidential campaign slogans gotten shorter?  Perhaps a low level of public interest in American politics and decreasing attention spans together have led to the public favoring the candidate with the shortest slogan.

In US history class I learned about the revolutionary "I Like Ike" campaign ad.  Television was a relatively new medium in the 1950s and was just beginning to see widespread adoption, and the commercial featured a catchy tune that stuck in your head, a short slogan, and visuals that subtly reminded you of Eisenhower's credentials.  Maybe each advance in media has further decreased Americans' attention span, and as such slogans have kept getting shorter each year until we hit the information limit of one syllable and four letters in 2008.  To address my question, I pulled a list of 200 US presidential campaign slogans from tagline guru, removed all of the "anti-" slogans, and then for each remaining entry marked whether or not that campaign was successful and how many syllables were in the slogan.  If slogans have indeed gotten shorter, then I should see a negative trend in their length over time.

Figure 1:  Syllable (left) and Character (right) length of US presidential campaign slogans.  Winning campaign slogans are in green, losing in red.  If multiple slogans were used by the same candidate in the same campaign, then all are included.  

Figure 1 shows scatter-plots of syllable and character length of US presidential campaign slogans versus year.  I have not included trend lines, because the scatter is obviously so great that the result wouldn't be particularly meaningful.  The length of successful or unsuccessful presidential campaign slogans does not appear to have changed much across the last two centuries of US history.

Figure 2:  Histograms of  syllable (left) and character (right) length of US presidential campaign slogans.  Green represents winning slogans, red represents losing slogans.

In figure 2, I have produced a chart of the relative frequency of each slogan length hoping to find some evidence that Americans have historically had some preference of shorter versus longer slogans.  In fact, a t-test indicates that the average winning slogan has on average 7.35 syllables and the losing slogans have on average 6.51 syllables, with p=0.05 (this means that the probability that the means of these distributions are actually the same, and this result occurred from random chance alone, is 0.05, or 1 in 20).  On the other hand, the average winning slogan has 25.7 characters and the average losing slogan has 23.6 characters, with p=0.15.  The large p-values and the similar means indicate that there is probably no preference between longer and shorter slogans.  If there is a preference, however, it is in favor of longer slogans!

So, US presidential campaign slogans have on average remained the same length throughout American history, and there is weak evidence (p=0.05) that Americans prefer syllabically longer campaign slogans to shorter ones.