[EM] IRV - how many candidates per party?

[Toplak Jurij]

There are several IRV experts on the list. I am sure you are aware of its practical use, too.   I'd like to know, how many candidates are usually offered by the same party in IRV? Only one? Two or more?   IRV is used in San Francisco and some other places. Since US has two-party system, offering only one candidate per party makes the total of two candidates. If there are two candidates, there is no difference between FPTP and IRV, right?   Does anyone know of any empirical study of practical use of IRV? Any comment is welcome. Jurij