A caucus is a voting event where party members attend a meeting to nominate a candidate for a general election. Any or all candidates can run in a caucus state, such as Iowa, and the winner is assigned all the delegates to the convention. A caucus traditionally requires physical presence, which is not conducive to overseas voting.
Some states, such as Iowa, have multiple caucus locations and even some abroad. To see if you can caucus abroad for your state, go to your state’s website for more information. You can find your state’s website by going to the State Voting Requirements page and inputting your state. Then, click the tab “State Lookup Tools”, and you will see a link for your state’s elections website.
You may also wish to check your state’s political party website for further information.