if you consider yourself poly...i find it interesting you use the phrase "the one". i suppose i could call my spouse, "the one" because i love him and im married to him, we have children together, we share a home, we are committed to staying together....but if you purely mean that emotional, i also love and am comitted to my boyfriend so there is not a "one".
If no one is poly, and nothing can happen...i have to agree with earlier posters its a crush and you move on. I'll admit, i crushed pretty hard on BF before asking my spouse to be poly...but i asked for the whole kit and kaboodle..and i already knew BF was down for it. (hes married and also poly)
keep on keeping on