First things first

Senate Majority Leader Harry Reid moved swiftly to ensure that his home state of Nevada wouldn’t be hurt by Medicaid changes included in the health care reform bill moving through the Senate Finance Committee. Politico

Whatever reelection in Harry Reid's home state of Nevada takes, that surely is what's driving him as a Republicrat majority leader.  Even though he presides over a comfortable majority in the Senate, he appears to persist in governing well to the right, pleading politics and pragmatism.

Nate Silver is working on his updated Senate rankings.  Here's what he has for Reid.

Nevada (D-Reid)- He's now tied with or trailing what amount to generic Republican opponents in many polls. He'll have money and organizational firepower, but not sure if it will be enough -- he's a big target -- and I don't see what narrative angle he's going to take to turn things around.

For pretty much as long a Harry Reid has been majority leader I've wished that his party would toss him and put in someone more deserving and effective.  I think Harry Reid is working against anything which could cost him his seat.