When our founders wrote the Constitution, they provided for a Judicial branch of government to insure that the laws of our country and the actions of its citizens were in full compliance with the Constitution. If those citizens felt that the existing Constitution was either too constrictive or not restrictive enough, they allowed for a process to amend it.
Liberal Democrats however, have always felt that the process of amending the Constitution was too burdensome, and instead, they believe it should be more of a "living" document; subject to broader Supreme Court interpretations based on the will of society at the time of their decisions. Of course, their definition of the "will of society" is almost always based on the will of Democrats and not necessarily society as a whole. Most Republicans believe that Supreme Court decisions should be based on the Constitution as written.
This fact was clearly found to be the case in a 2014 Pew Research poll on the subject. 70% of Democrats said that the Constitution is subject to interpretation based on current times. On the other side of the political aisle, 69% of Republicans felt that the Constitution should be interpreted as written. Among Independents, the issue was near equally split.
Now, with the death of Justice Scalia, President Obama is the recipient of the Democrat's dream of a lifetime by being able to tilt the Supreme Court to a liberal bias; and, in doing so, insure that the court starts making decisions by putting their political fingers in the air in order to sense which way the Democratic party's political winds are blowing. Thus, instead of the Court being truly blind, it will become an extension of the Democratic Party. That's a very dangerous thing; not just for Republicans, but for the country. With the court having a liberal majority, laws passed by Republicans will surely be struck down, and laws written by Democrats will be automatically upheld. Is that what we truly want from our nation's highest court?
Lastly, before Scalia's death, and at a time when the Supreme Court was dominated by conservative Justices, Gallup asked if people thought the high court was too conservative, too liberal, or just right. In response, only 20% thought the court was too conservative. 40% thought it was just right; and 37% thought the existing conservative court was too liberal. My guess is that poll will be substantially different if Obama gets his way. And, it won't just be 37% liberal bias.
The Living Constitution: http://www.law.uchicago.edu/alumni/magazine/fall10/strauss
Americans divided on how the Supreme Court should interpret the Constitution: http://www.pewresearch.org/fact-tank/2014/07/31/americans-divided-on-how-the-supreme-court-should-interpret-the-constitution/
Polling Report: Judiciary: http://www.pollingreport.com/court.htm