BP 

First of all, I understand that you have a stake in this article.  You've put a lot of time and effort into it and you don't want to see it deleted.  I had an article deleted once, and I understand the frustration that you feel.  

If you read what constitutes a notable organization in WP:N and WP:ORG, it doesn't really meet the criteria set forth.  Yes, you've provided some sources that mention the Bulldog Party, but they aren't really considered, Significant coverage which means, "that sources address the subject directly in detail...".  Also, WP:ORG states "Organizations whose activities are local in scope are usually not notable unless verifiable information from reliable independent sources can be found," however, it does say that, "The organization’s longevity, size of membership, or major achievements, or other factors specific to the organization may be considered."  The Bulldog Party may have been around in some form since the 1950s, though, so maybe that might help  if you can prove it. 

The possible longevity and the "major achievements" and "other factors specific to the organization" is where you stand the best chance of defining why it's notable, because of this statement in the article, "The Bulldog Party has inspired the formation of other student organizations on universities throughout Missouri, most notably the Bearcat Voice at Northwest Missouri State University and the Student Progressive Party at Lincoln University (Missouri)."  However, this isn't sourced at all, and quite frankly, it's questionable whether the Bearcat Party article meet the notability criteria as well.

If I submitted this article to AFD, would it definitely get deleted?  Most definitely not.  There's a good chance that it would, but it's not a given.  However, no one could make the argument that it's good enough as it is and its notability shouldn't be questioned. 

Why has no one else brought this up before since you first created in March 2005?  Probably because it hasn't attracted a lot of attention and overall, it's well-written.  There aren't many other articles that link to it, so unless someone stumbles across it through those links, the only other way someone will find it is via Random Pages (unlikely with over 2 million other articles) or through Recent Changes (and since there have been barely over 50 edits in 3 years, that's not likely, either  especially if the edit wasn't vandalism).

Keep in mind that none of these arguments make an article notable or worth keeping:
 I like it... or It's interesting....
 It took me a long time to write....
 This other student political party has an article....
 It looks good... or It doesn't do any harm...

I'm not going to submit this article to AFD, but you really need to work on getting it fixed (if possible), because it's likely that someday someone else will come across it and come to the very same conclusion that I did about it.   Good luck, and happy editing.