The Republicans seem to be the major opposition to the bailout bill. Seems they don't want to go home to their constituents and tell them that they helped the Bush administration ram through a $700 billion bailout package. The package isn't as bad as it sounds--but anything more complicated than "I'm giving you money" is hard to explain from the stump.
Of course, we don't actually know exactly what's in the package, except that the Democrats seem to have put Paulson on an installment plan. So it's hard to know exactly what they're turning down.
By walking out, they get to hang the responsibility for the package on the Democrats--it probably won't be much more popular with their constituents. But without the Republicans, the plans costs are certain to go up considerably, including, probably, giving bankruptcy judges the power to rewrite mortgages. This sounds wonderful--until you realize that this means mortgage rates will go up for everyone, probably quite a bit. And that this will further strain an already weak industry. Why use jinglemail, or struggle to meet your payments, if you can pay a lawyer $1,000 and magically transform your mortgage into a prime loan?