Obama and Biden are members of the Senate. Obama saying "I'm running for the highest office in the land" is not good enough. He is paid to be a Senator and this isn't just a garden-variety sewage treatment plant bill. These are serious times and SENATOR Obama should be doing his job, not merely "letting the Senate do what it's supposed to do". He sould be doing what HE's supposed to do.
That argument doesn’t fly — everybody knows that it’s routine for Senators and Congresscritters to go on the campaign trail (if only for reelection) while continuing to do their jobs.