Clark Lindsey notes (probably correctly):

Certainly one way to help insure that the exploration program continues past this administration would be to tie it closely with international partners as was done with the ISS in the early 1990s.

Based on history, it would also be a good way to insure that the program is delayed, over cost, and doesn’t achieve its objectives. Back in 1993 NASA made a Faustian bargain. It would accept the need to make the station more “international” in exchange for keeping Congressional (and in that case, more importantly, administration) support. It won its appropriation by a single vote.

We went to the moon alone, and it was vastly successful, at least in terms of getting to the moon. There’s no reason to think that bringing in other nations increases the probability of success, or reduce costs, even if it increases the probability of keeping the program alive politically. This is not a dig at other nations–it’s simply a recognition of the degree to which bringing in other entities, with their own inscrutable politics (that, like ours, largely have nothing to do with space), can complicate and confound our own efforts. For recent (in the last four years) readers of this blog, I discoursed on this subject back in 2002.