Achallenge that modern presidents face is

Criticism, because he's a leader. lots of people blame him because he makes tough calls. he is also involved in forien affairs, so of something goes wrong people blame him when it could be the senate. the presedent also most likely has a diffrent opinion then most of congress. to become presedent he had to put his life out for everybody to see. he has to balance the roles of being a political leader and social leader.

They made a checks and balance system to equal power within the branches. the "check" meant that one branch would watch one branch and "balance" them if they were too powerful. if you want more info on this, i would just google checks and balance system.