The Constitution doesn't say the Senate has to vote on appointments. That's your first error. The sum and substance of what Article II, Section 2, says about appointments to high offices is as follows:

He [i.e., the President] shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments.

The only statement made is "by and with the Advice and Consent of the Senate". So what do Constitutional scholars say about this? Well, let's see what Constitutional scholar Barack Obama said about the meaning of this on January 26, 2006:

As we all know, there's been a lot of discussion in the country about how the Senate should approach this confirmation process. There are some who believe that the President, having won the election, should have the complete authority to appoint his nominee, and the Senate should only examine whether or not the Justice is intellectually capable and an all-around nice guy. That once you get beyond intellect and personal character, there should be no further question whether the judge should be confirmed.

I disagree with this view. I believe firmly that the Constitution calls for the Senate to advise and consent. I believe that it calls for meaningful advice and consent that includes an examination of a judge's philosophy, ideology, and record. And when I examine the philosophy, ideology, and record of Samuel Alito, I'm deeply troubled.

Obama didn't stop there, though. He attempted, unsuccessfully, to filibuster Alito's appointment, even though there were nearly 3 years left before Bush left the White House. I am aware that on or about February 16, 2016, he expressed "regret" for this. If you're like me, you're going to treat Obama's ex post facto "regret" over this statement like the self-serving political statement it is - he had ten years and 21 days to clear up the record but only seemed to feel a pressing need to do so after Justice Scalia was dead and his statements could come back to haunt him.

But you know what? Constitutional scholar (as opposed to President) Obama was right. We have a balance of powers in the United States. The Senate's advice and consent is required to pass a Supreme Court justice. The Senate has refused the President in the past, so it's clearly not acting in an "unprecedented" manner to refuse the President now.

Democrats are also trying to spin the statement that Chuck Schumer made in July 2007 to declare that no new Bush appointments should be made except in "extreme circumstances". This was a completely unnecessary statement addressing a highly theoretical problem, and it was made at a time when President Bush had 18 (!) months remaining in his second term.

I think we are all well aware that if Obama were to choose a conservative justice who believes in legal principles similar to those espoused by Scalia, or even, honestly someone closer to the center but on the right, the Senate would take the time to review the candidate properly and hold a vote. However, we know that Obama won't do that. I am not even sure Obama will pick the most qualified person for the job. I think he will pick a moderately qualified person who is also (X), where X=some targeted ethnic or religious group that Obama wants to see represented on the court, because the phrase "identity politics" is a fair summation of the Obama Presidency's approach to race relations. Incidentally, I think it's a large part of why race relations seem to have deteriorated in America.

The Republicans are certainly not going too far. Politics is first and foremost about power, and secondarily about ideology. Ceding Scalia's seat would upset the entire power balance in American politics, and Republicans will (and should) take any steps that are not unambiguously illegal in order to stop Obama on this issue. Democrats can come up with 500 wonderful arguments (though I note they have yet to come up with one even remotely compelling one) purely and logically set forth, with all the rhetorical eloquence that they can muster, and it will not change A DAMN THING. We will fight them on the land, we will fight them on the sea, we will fight them in the Congress, we will fight them in the courts, we will fight them in the counties, we will fight them in the cities, in the fields and streets and we will never surrender.