Nearly seven in 10 college students have watched a video about a presidential candidate on YouTube, according to results of the CBS News/UWIRE/Chronicle poll of undergraduates.

The poll, the results of which were released yesterday, is a Web-based survey completed by nearly 25,000 undergraduates at 49 four-year colleges in four battleground states: Colorado, North Carolina, Ohio, and Pennsylvania.

It turns out that the free time candidates are getting to air their messages through their videos on YouTube may be worth millions of dollars to the campaigns, according to analyses reported by Micah L. Sifry on the Web site Techpresident.com.

Mr. Sifry wanted to find out roughly how much the candidates would have had to pay to have to disseminate their video messages that appeared at no cost on YouTube on the television airwaves.

First, he asked David Burch of TubeMogul, an online-video analytics and distribution company, to estimate how much time each candidate’s messages had been viewed, by multiplying the number of their videos by the number of individuals who viewed each and the length of time of the video.

The total viewing time for Barack Obama’s videos came to just over 14.5-million hours. The time for John McCain’s videos was just over 488,000 hours.

Mr. Sifry then asked Joe Trippi, a political consultant who has worked for Democratic presidential campaigns, to do the math of how much it would have cost the Obama campaign to buy television advertising for that much time. His answer was about $46-million. Using the same math, the cost for the McCain campaign for his time would be about $1.5-million.

Mr. Trippi did note that the comparison is not completely apples to apples, since a TV ad is a form of “push” media that interrupts people’s attention, Mr. Sifry wrote, while Web video is much more a “pull” media, where we choose to watch.