I'm applying to developmental psych phd programs and I've run into what seems to be a common problem: no idea who to ask for my third LOR. The first two are fairly obvious. One is my senior thesis sponsor; she's very familiar with my research skills, very supportive, and extremely well known and respected in the field. The second is an adjunct professor I took an honors class with; he's become a sort of mentor, is very familiar with my writing, and I know he thinks quite highly of me.
So then there's the third. While I've developed great relationships with the two mentioned profs, most of my other professors barely got to know me. Because I switched to psych relatively late (junior year) I had to catch up with a lot of lecture classes, so my opportunities to get close to profs have been slim. I have three main choices:
1) Former neuroscience prof who is also director of the senior thesis program. I got an A-, which is good for his class, but did no writing in the class. However, he will have the opportunity to become familiar with my writing because he must approve thesis drafts. The problem is I'm just getting started and don't know if I'll be able to submit my intro draft sooner that it's due (somewhat late in the semester).
2) Former social psych prof who got to know me by name. I got an A in his class and submitted papers, but the TA graded them. Of course I could show him the papers when I asked for the LOR.
3) Research methods prof who I did not get to know, but for whose class I wrote considerably more intensive papers. Again, the TA graded them.
I know my third LOR will be considerably weaker than the first two, so I'd also appreciate any insight into how much the strength of the first two can counteract that weakness.