Brownback's a non-starter. I saw him on the NewsHour shortly after Alito's nomination, and he was pitiful. He was a guest along with Dick Durbin, and Durbin was in non-stop slander mode, saying that Bush caved to the "far right" nominating someone so far "outside the mainstream" - the typical Democrat pap on judges. And Brownback never directly challenged any of it. He just let Durbin make monkeys out of conservatives without standing up for them at all. I completely wrote him off after that. Whatever "correct" positions he may have taken, he's useless if he doesn't actually lift a finger to stand up for them.
As for Allen, if he's so much like Tancredo, then why do you think he has a better shot at the nomination than Tancredo does?
Brownback and Allen are serious candidates, Tancredo is not very bright and he has a penchant for coming unhinged. I'll never understand how the guy made it to Congress.
And BTW, Bush DID cave to the far right in junking that Miers woman and nominating Alito -- and thank goodness he did!