The strong cover letter should be supplemented with follow-up contact.   Lay the groundwork in the cover letter. Attached is my resume for your review.  I will send my [recommendation letters, transcripts, latest writing sample] within the next two weeks.

Consider being bold.  In your letter to the decision maker’s assistant, state that you will follow up to determine convenient times for brief meeting.  Yes, this approach is a bit aggressive but out of 100 letters sent, you may be successful in setting up three meetings and one of those meetings may lead to a job offer.  It did for me.