Donald Trump is going to be an amazing distraction. (And full disclosure: One of us, on “Daily Rundown” yesterday, fully participated in that distraction with Trump.) On the one hand, if you’re Mitt Romney, you probably like this. Trump — at least from now until June — takes oxygen away from Tim Pawlenty and Haley Barbour. On the other hand, Trump and his “birtherism” obsession diminish the field and the party. We’ve said this before, and we’ll say it again: No other Democratic presidential candidate (or NON-candidate) ever overshadowed Obama or Clinton in 2008. But the theme so far to the 2012 race has been that a lot of Republicans — whether it’s Trump, Michele Bachmann, or even Buddy Roemer (at one forum) — have already overshadowed the top-tier candidates.