The nuclear option is a game of chicken. Democrats fear being in the minority in the Senate, so they don't use it. Republicans fear being in the minority in the Senate, so they don't use it. However, if Democrats attempt to obstruct a Republican President the way Republicans have obstructed Obama, what are the chances that you think Republicans would pull the trigger on the nuclear option? What if Republicans were trying to replace a Supreme Court Justice like RGB with a Scalia type justice? Would the Republicans pull the trigger on the nuclear option?
My feeling is that they would absolutely pull the trigger.
Basically, the obstructionism in Washington has gotten so bad, that eventually one side or another is going to pull the trigger, and whoever does it first is going to be the one who benefits the most. There is no point in letting Republicans pull out the nuclear option first, when we would have REAL justification to use it with Clinton attempting to nominate a Supreme Court Justice. After all, if Democrats are using the nuclear option on Supreme Court picks under a Clinton administration, they can easily argue that Republicans have no intention of allowing a Democrat to nominate ANYONE to the Supreme Court that is not ultra-conservative (basically someone they would pick themselves). This would clearly be true after blocking Garland's nomination. The Democratic Party would be on solid and firm moral ground to pull the nuclear trigger.
If we allow Garland to be confirmed at this point we are only rewarding Republicans for their obstructionism. After all, their plan is literally to hope that Trump wins so they can appoint who they want to the Court. Failing that, they will accept the compromise. This is not how the system should work. Had they engaged the process in good faith, rather than attempting to have their cake and eat it too, then we would be having a different discussion. Rewarding them will only encourage this type of behavior in the future.
...and let's be clear, Democrats should not be acting this way, either. We actually need to have a functioning government regardless who holds the Senate, the House, or the Presidency. If someone is democratically elected, then the people have given them the authority to govern, and the democratic will of the people should be respected--even when we disagree with it.