My partner is asleep, else I’d have him chime in.
He’s an associate professor, and is qualified in terms of time to apply for full professorship; he’s lacking in two publications.
It’s not always the case where the associates are competing for a limited number of slots; as with gaining tenure, one goes from associate to full professor by fulfilling particular requirements set out by his or her department, and the uni or college in general.
My partner is at a 4 year college with a teaching emphasis, so his requirements are not as publishing heavy as one might find at a research-orientated institution.
Nevertheless, for him to qualify should he decide to go for full professorship, he has to have completed a certain number of years at the associate position, which, I think is 5 at his school, and at least 12 years of teaching total. He does have to have a wee bit of publishing or conference attending, committees participated on/chaired – things that demonstrate professional development.
No one at his school could go straight from PhD to full professor in a year. In addition to the publishing and professional advancement requirements, there is also a question simply of being an assistant professor for X number of years. And then X number of years to become full.
There are some exceptions; sometimes one goes backwards – for example, if you are a full professor at Uni X, and you wish to take a job at Uni Y, you might get ‘busted down’ to associate professor for a year, or maybe you can accept the job only if you agree to be an associate for a year. Also sometimes you will be offered a job at uni Y at a higher rank. Although you can be busted – one of my music profs was a full professor who finished his career as an assistant professor when it was discovered that he had not paid a single royalty for the uni choir in something like 10 years, and the school owed about $20,000 in fees and fines. In exchange for not sacking him, he agreed to go to a year to year contract as punishment. It was extremely humilitating for him, as everyone knew, but he was still too young to retire, and the fiasco too well known for any other school to hire him.
Some professors never apply for full professorship, so it’s not a matter of ‘not making the grade’ – it depends on your own motivation and not all schools have a limited number of slots. His school allows as many full professors who want to be and who qualify. Also, to go to full professor, the committee isn’t all full professors, but tenured professors (so it can be your peers. At his school, there has to be at least one full professor).
At his school, it’s more than one level of judgement – it starts with departmental committee, then department chairman, then the dean, then there is usually someone between the dean and president, like the provost or VP, then the president, then the board of trustees/visitors, etc.
I have no idea how he got through; apparently none of them have ever met him, I suppose. 
Seriously, though, it’s not as difficult as it sounds. If the department is honest with new PhDs, the PhD will know precisely what is expected of him or her to get promoted. So you know all the hoops, and it’s not a guessing game…he says, unfortunately not all departments are honest with their faculty…