I was responding in the first instance to your association of McCain to the S&L scandal, to Obama's association with Rezko, however, I base my assessment of Obama's character to more than his association with Rezko. But let's examine and compare the two instances.
McCain has admitted that what he did was wrong as it gave a wrong appearance of undue influence, McCain was mildly rebuked by the Ethics Committee for having exercised poor judgment, and later worked successfully to pass bipartisan campaign finance reform. By contrast, Obama sought and received $120,000 from Rezko during his 2004 Senate campaign and also asked for his "favor" to help him buy his house and two parcels of land cheaply, knowing that at the time, Rezko was under investigation by the US Attorney and the FBI for bribes, kickbacks, and "efforts to illegally obtain millions of dollars."
As to the SCOTUS, as I said, I don't believe, based on McCain's past record, that he would choose another Alito as a nominee. Assuming he does, however, it would be up to the Democratically held Senate to reject that nominee. Assuming they don't, then the onus is on them, it seems to me.