"at least 5 current Republicans are extremely vulnerable and blocking the appointment could alienate enough voters for the Republicans to lose those seats and with them"
Yeah, or they could not block the appointment and alienate their entire stinkin' base ahead of the election, giving up both senate/house seats as well as the White House. According to this logic, there is nothing the Republicans can do to avoid losing control of the senate, despite widespread dissatisfaction with a full eight-twelve year of Democrat rule, and outgoing second term president, economic malaise, and a foreign policy satisfactory to exactly no one.
If this man's death truly carries this kind of strategic value (guaranteed senate control & probably the presidency) then yeah, I can see somebody offing him
"Yeah, no matter who Obama nominates, they will not be confirmed"
I agree; were there not one, not two, but three senators running for president (three; three senators; ah-ah-ah...) who
really want the appointment all to themselves, then I'd be a whole lot less certain. But between Obama, Cruz (especially) and Sanders, avoiding a filibuster is impossible;
-Liberal nominee; not only is Cruz/Rubio opposed, not only is he willing/able to block it (Cruz at least is), he will look like an absolute hero for doing so
-Moderate nominee; will be savaged by both Cruz and Sanders (probably simultaneously; would be very humorous to watch) as insufficiently principled, and will damage support on both sides so badly no filibuster will be needed
-Conservative nominee; provided Hell freezes over, Sanders and about twelve other senators would take turns filibustering
-Multi-ball Siege; If Obama pummels the Senate with appointments hoping to wear down the opposition (forcing endless filibusters), he will quickly wear out McConnell's patience & be entirely blocked, regardless of the type of nominee, and the blatant use of the process as a political weapon will galvanize republicans to opposition. Even 'squishy' or 'establishment' Republicans would line up to heroically block the umpteenth appointment vote & establish their street cred (if McConnell were wise, he'd have them all take turns as a 'team-building' exercise before finally shutting off the floor votes)
-McConnell keeps his word, and doesn't bring nomination votes to the floor. I see this as unlikely, as Obama hasn't been stalled for a year on anything, ever. But it's still possible.
Personally, I expect a liberal nominee set up to be a sacrificial lamb (Lynch) for Hillary to heroically defend, then a more pragmatic choice of what Obama considers a moderate closer to the election (he'd obviously still prefer to get one last nomination through to cement his 'legacy' regardless the politics), but I doubt he's capable of choosing someone even remotely tempting for Republicans (even if they've been savaged by the media & all their DC neighbors for a solid year about it). In short, there is nothing to worry about, since Obama can't force a floor vote on his picks; he/the media will moan for a few weeks about 'those mean old bullies' then they will move on after they get bored.
TCB
It seems at best a 50/50 proposition. 
