The Donald is just going to try and rough up, damage and distract Obama while the R's figure out who to run for real.
Palin, Romney, Trump, Paul will all be distractions floated to draw fire away from the eventual real candidate.
I saw an interview with Trump where he categorically stated he would not run if it meant drawing votes away from the Republican nominee, causing Obama to win. We'll see if he is a man of his word.