I have been saying this for a while now, so I might as well put it down in writing: Of the announced Republican candidates for president, there are only two who can credibly win both the Republican party's nomination and the general election: Mitt Romney and Tim Pawlenty.
I take a historical view regarding these things. History teaches us much, if we are willing to learn from it. And here is what history teaches us: Members of the House of Representatives do not win presidential nominations, or if they somehow manage to do so, they do not win the general election. I believe there is exactly one exception to this rule, Abraham Lincoln, in our nation's history. And that was roughly a century and a half ago. (Note: John Quincy Adams was elected the House after his presidency, but he had been a senator prior to that.) Based on this, Rep. Michele Bachmann will not be the nominee. Maybe the VP nominee, but not the presidential nominee.
Likewise, Rep. Thaddeus McCotter will not be the nominee. Nor will Rep. Ron Paul be the nominee. Nor will former representative Newt Gingrich. (Although Gingrich was more than just a congressman, he was speaker of the House. Still, his campaign is in tatters, so we can safely disregard him anyway.)
The presidential nominee is almost always a former or current governor, a former or current senator, a former or current vice president, or a war hero general. As in, very close to 100% of the time. David Petraeus and Norman Schwarzkopf are not running, so we can rule out the war hero general possibility. Dick Cheney and Dan Quayle and George H. W. Bush are not running, so we can rule out the former VP possibility. So we are down to former/current governors and senators.
Therefore, the possibilities are: