In the United States today, the political parties’ official platforms, written at the national conventions, mean very little or even nothing. These are not things that individual candidates must adhere to and they are given essentially no attention in the campaigns. They are essentially a holdover from a time when they did mean something.
In our system today, it is very difficult for political parties to maintain discipline over their members. The people who run for Congress as Republicans (for example) are not picked by the party leadership. They are, instead, picked by the voters in primary elections. Therefore, if they do not want to follow the party platform, there is very little that the party can do about it. We have seen in recent years many examples of “tea party” insurgents defeating Republican incumbents in the primaries even though the party supported the incumbents.
Because the party cannot force elected officials to adhere to the party platform, it tends to be ignored. Candidates tend to campaign on whatever issues they think will be most effective in getting them elected. They do not simply say “elect me and I will carry out the party platform.” Therefore, party platforms are not any longer important in the US system today.