The fact that your project proposal stipulates that you are looking for a permanent writer for your blog leads me to infer that the primary concern for you - with the axiomatic exception of the possession of the talent and ability to actually fulfil the requirements of the role - is that the person you eventually hire is professional, consistent and reliable.
We'll get to my considerable literary talents in a moment. For now, allow me to assure you that I will deliver all mutually agreed upon, flawlessly written and meticulously proofread materials on time and to your complete satisfaction. I am a professional and, although new to this site, I have a verifiable record of hitting deadlines and surpassing even the most scrupulous expectations.
I have been writing professionally for over a decade and my extensive experience is matched only by my prodigious talent. I know what it takes to produce quality content that converts and I am the king of the call to action.
I am certain I am the best candidate for this job. I have the talent, the relevant experience, the appropriate skill set, and an unrivalled determination to succeed in creating the best version of your project...the version you dared to hope for when you initially considered posting it.
Good luck and I hope to hear from you soon.