Even though in the past, he has said that the constitution is a "living, breathing document" and that it's policies are subject to evolution, I firmly attest that the constitution needs to be adhered to for the welfare of this country, and the constitution clearly states that it is the responsibility of the president to make a nomination when a vacancy occurs. If the senate finds that nominee to be unfit for the job, then they can have the last say, but trying to stall the nomination is ridiculous.
The Republican Party are incorrect that President Obama does not have the right to nominate a Supreme Court justice. Trump's argument that an outgoing president hasn't done so for more than 80 years is not an argument in itself. The argument of the Republican Party seems to be based on a foregone conclusion that their party will win the election. This is by no means set in stone but Obama is the current president. By that reckoning, he has far more authority to make this decision than any of their potential candidates at the current time.
President Obama should nominate a Supreme Court justice before the end of his term. It is his right and obligation. The Senate also should take up the matter and hold hearings to keep their commitment. Blocking the nomination sets a bad precedent, and one that will not be forgotten for a long time.
It's the president's job to appoint a new Supreme Court justice when one dies or resigns. Barack Obama is the president. He should appoint a new Supreme Court justice. It's very simple. The people who think he shouldn't don't seem to have any legitimate arguments; they just don't want a liberal-leaning justice.
The Constitution has specific provisions for nominating a Supreme Court justice. There is nothing saying that because his term is up soon that he shouldn't do it. The Republicans making the suggestion to delay the nomination are clearly ignoring the constitution and trying to paint President Obama as a figure that is "less than" other Presidents. It's insulting, a bit racist, and downright wrong.