New collumn with mutate and ifelse but keep NAs in R

I have a simple question but it is giving me a hard time. I wish to recode a varibale with a ifelse function but I want to keep the NAs (in the variable "party") as NAs.

This is what I am doing. I have a variable with vote choice ("party") and I want to recode a new variable ("RRP") if participants choose a specific set of parties:

df<- df %>%
  mutate(RRP = if_else(party %in% c("4",#SPP/UDC
                                    "12",#Swiss Democrats
                                    "13",#FDU
                                    "14", #PSL
                                    "15"), 1, 0))

The problem is that participants who have NAs in the "party" variable are now being recoded as 0 because they don't fullfil the condition in ifelse.

I also tried this:

df<- df %>%
  mutate(RRP = if_else(party %in% c("4",#SPP/UDC
                                    "12",#Swiss Democrats
                                    "13",#FDU
                                    "14", #PSL
                                    "15"), 1, 0,  na.rm=TRUE))

but it just yield an error. Do you have any other ideas?

Thanks a lot!