Sure you can. If the election were today, Rudy would beat Hillary or any other Democrat according all the recent polls. For the past few weeks, Rudy has consistently held a beyond-the-MOE lead over every Democrat. No other Republican can claim that.
Of course, that is no guarantee the lead will remain through the general election.
We should also think ahead to what the media will be covering in the summer of 2008. Rudy has a lot of personal baggage that hasn't shown up yet in voters minds.
The media is going to savage any Republican nominee. Even if their record is squeaky clean, the media can manufacture a controversy. I'm not sure that the "revelations" against Rudy will be as damaging as some think. A lot of voters already know and seem willing to shrug it off. Rudy is also insulated from the hypocrisy charge because he makes no claims to be a saint. In a lot of cases, the hypocrisy is more damaging than the revelation.
That being said I do support a Fred candidacy.
From what I know of Thompson, his views are very similar to mine. I'm just not as convinced as many that Thompson (or any other conservative) can win the general election in the current electoral climate. It is not 1980 or 1984. In my mind, beating Hillary or Obama trumps the other concerns in this election.