With all of the talk about inevitability and momentum, Gallup and USA Today decided to poll on how a Mitt Romney/Barack Obama matchup would look to registered voters in the fall.  The good news for Romney?  Six in ten declared themselves satisfied with that choice in November.  The bad news? Well ….

Six in 10 registered voters would be satisfied if Barack Obama and Mitt Romney become the nominees for president this year, while 34% say they would not be satisfied. Democrats are most likely to say they would be satisfied with these two candidates, while independents are least likely.

That actually understates the finding.  According to their breakdown, 81% of Democrats find this a satisfactory matchup, as opposed to 60% of Republicans.  Only 44% of unaffiliated voters find this satisfactory, though, with 47% unsatisfied.

The dynamics of the race explain at least some part of this, of course:

Democrats’ satisfaction with an Obama-Romney ticket (81%) reflects the reality that Obama has no competition for the Democratic nomination as he seeks a second term. A smaller percentage of Republicans (60%) would be satisfied, but the fact that it is still a majority suggests Romney has the potential to rally his party’s followers behind him if he becomes the nominee.

Independents by definition are not attached to the parties, in contrast to those who initially identify as Democrats or Republicans, helping explain why independents are less likely to be satisfied with a choice of only two major-party candidates.

This also explains why, as I remind readers occasionally, head-to-head polling at this stage of the cycle is not particularly predictive.  The reason for the lower satisfaction among Republicans is because they have other options than Romney at this point, while Democrats do not.  That’s also why Republicans poll lower in head-to-head surveys against Obama.  The actual key in those surveys is Obama’s support level, and even that is probably overstated to some degree, thanks to the necessary debate taking place in the GOP primary.

That’s why the second part of this survey is the most interesting.  If it comes down to these two choices, 88% of Democrats and 80% of Republicans will choose one of the two.  However, when taken as a whole, only 35% of the sample of registered voters are either certain or likely to vote for Barack Obama, and only 22% of the independents.  That’s a remarkably low re-elect number for an incumbent, especially a Democratic incumbent in a registered-voter sample.  In contrast, while in the middle of a tough primary fight, 32% say they will vote for Romney, including 27% of independents — and that would be higher if not for 31% of Republicans who didn’t commit to voting for Romney if he was the nominee.

Obama, of course, is the known and non-variable quantity in this political equation.  Only having 35% as a solid foundation is a prescription for disaster as Republicans unite around a single candidate.