Not true about unemployment. If unemployment isn't below 7.5%, Obama is toast. Anyone could beat him whether it's Romney or Tom Delay. Also, don't underestimate the GOP's ability to make ads stating that our tax dollars should go toward defeating the terrorists and not towards their defense attorneys.
There are factors in existance beyond Obama. The question may well be undivided control of the national government by the GOP given the high prospect the GOP would take the senate in 2012. That gurrantees Obama 46% and probably close to 152(MA,NY,VT,RI,DC,MD,CA,WA) electoral votes regardless of economic conditions. To be fair though, this issue is probably weakest with someone like Romney. On the otherhand, against someone like Palin, well, if Obama converted to Islam tomorrow he would still have difficulty dropping below 200 or so electoral votes.