A reporter covering congress will probably try hardest to get an interview with one of the party leaders
if you're using plato the answer is *one of the party leaders
One of the party leaders
Explanation: A reporter who is covering Congress will probably try its best to get an interview of the person that is the member of the same party that he is covering.
If he gets an interview of the person that is one of the party leaders of Congress will be great work because member from the party will know the party in the best way.