Many states' polls are all over the map, but Mitt Romney is close to Obama or ahead of Obama in Michigan and Pennsylvania. Furthermore, Obama is underwater in approval in these states. Being underwater in approval doesn't guarantee an Obama loss, but a credible GOP candidate can flip a state where the president is underwater in approval. To be credible, a candidate has to have the right mix of experience and be able to talk about the issues clearly. Mitt Romney has that experience and can speak clearly. I understand that everyone on Free Republic sees Mitt Romney as the anti-Christ. You'd rather re-elect Obama than vote for Mitt Romney. However, your wishful thinking that Mitt Romney can't win these states doesn't change the fact that he can both. He is certainly more likely to win one or both of these states than Herman Cain is.
John McCain was popular in New Hampshire relative to other Republicans, but he was still a pathetic candidate. Against Barack Obama, he appeared old and out of touch. New Hampshire voters are not as enthralled with the cowboy image that some conservatives think is necessary for someone to be a conservative. Republicans have had a hard time in New Hampshire because most recent Republicans have had that image. Mitt Romney won't have that image problem, so he has a good chance to win New Hampshire.
Mitt Romney has made numerous trips to Nevada and won the caucuses there easily in 2008. In spite of what the Romney haters think, many conservatives either like Mitt Romney or would at least rather have him than have Obama for four more years. Those who are still comfortable in their jobs and haven't lost too much value in their homes can hide behind their keyboards, whine about things that Mitt Romney has said in the past, and insist that they'd rather have another four years of Obama. Huge numbers of Americans in other situations don't believe that anti-Romney accusations and wouldn't care that much even if they did as long as Mitt Romney kept his promises to start making changes that will bring back jobs. They make a Romney win likely in Nevada in spite of the howling of the Romney haters.
Mitt Romney has also been active campaigning in Colorado and would have a good chance to put Colorado in play. Colorado has a bit of a yuppie demographic. Many of those people saw John McCain as old and out of touch and saw Sarah Palin as an idiot. I can disagree with them all day long about Sarah Palin, but my disagreement doesn't change the fact that they flocked to Obama. A credible GOP ticket and the poor economy would bring them back to the GOP. The Tea Party may be active in Colorado, but the gains among urban and suburban professionals would more than compensate for Tea Party types who hate Mitt Romney more than they want Obama out of office. Mitt Romney could win Colorado.
New Mexico is likely to stay in Obama's column, but his approval there is low. A credible candidate has a chance, but the Democrats may win simply because they will put resources into the senate campaign that you mentioned. Our choice of candidate probably doesn't affect the New Mexico outcome that much, but Mitt Romney does no worse than any others.
Indiana will almost certainly go back to the GOP. We lost Indiana only because people bought into the whole "hope and change" myth and because we ran a weak ticket. Winning Indiana shouldn't be consideration.
Florida should go back to the GOP because of Obama's positions on Israel, but we will need to be careful. Rick Perry will have a hard time winning Florida because of his statements about Social Security. For most workers, Herman Cain's 9-9-9 plan may not be so bad because wages may rise as corporations with lower tax rates use some of the extra money to compete for the best employees. For retirees, the addition of a national sales tax is a loss without any compensating gain. Cain's 9-9-9 will never pass the Senate anyway, but if we are going to admit that his plan cannot pass, then the rationale for supporting him as a candidate disappears also. Herman Cain and Rick Perry are the GOP's weakest candidates for winning Florida in the general election even though the "anyone but Romney" vote is making Herman Cain competitive in primary polls. Unless we can swing Pennsylvania and Michigan, we need to win Florida, and Mitt Romney has a much better chance than Herman Cain does.
The GOP will have to work to win Ohio again, but conditions are right for that win. None of our candidates will have a particular advantage in Ohio, and Herman Cain's Georgia background certainly doesn't make him "one of us" in Ohio.
North Carolina barely went for Obama in 2008 and should swing back to the GOP fairly easily. Even so, North Carolina has a large population of people who are highly educated and work in technology intensive jobs. They are more likely to relate to Mitt Romney than they are to Herman Cain. They certainly won't relate to Rick Perry.
Virginia will be like North Carolina, and the big population of urban/suburban professionals in Northern Virginia will also lean more towards a more educated candidate. Any Republican is going to have some problems with this population because reducing the federal government will eliminate many of the jobs that support the Northern Virginia sprawl. For image reasons, these people won't vote for Rick Perry. They probably won't have a big preference between Mitt Romney and Herman Cain.
Iowa is the only state where Mitt Romney would have a serious disadvantage against Obama compared to other Republicans. The religious conservatives will fall into the Jeffries style of anti-Mormon voting, and Mr. Romney's decision to skip the straw poll will bother the entire state.
Again, I realize that Free Republic is headed by and full of people who hate Mitt Romney more than they hate Obama. I realize that they'd rather have another four years of Obama than to see Mitt Romney become president. If that's how you feel, that's your right. However, the notion that Mitt Romney isn't the strongest candidate against Obama is silly.
Think in the end it will come down to Romney winning above the Mason Dixon line and Perry below it.
Cain will strip votes away from both Romney and Perry.