Hello there! the answer is the second option, Republican!
Whenever there's an election the United States, there are two major parties that you hear a LOT about, more than any other party, including: on news, in kids books and YA/Adult novels, in many jokes and memes, and they are Democrat and Republican. There are other parties, like the green party with Jill Stein running in the 2016 election.
Also, the Whig party was shut down in 1854, so this can't be it. As well as that, the Federalist party ended in 1824. I am not sure about the populist party, but it is not very popular and i couldn't find anything on it from research.
I hope this was helpful! Have a great day :)