I wouldn't be too sure of that. First of all, there haven't been any Republican votes yet. We're still a long way away from the first primaries and caucuses. And the polling right now doesn't mean much, what with seventeen candidates in the mix. Plus, Trump has the celebrity/name recognition thing going for him now, which doesn't impress me.
As for FR posters, there are many of us long-time conservatives here who do not trust Trump and do not support him and have not gotten on the bandwagon. I do not see a "prevailing opinion" here for Trump.
Trump's past and present liberal positions, plus his off-putting character, cause me to put him at the bottom of the list.
Oh, I don't know why not. To the extent such things can be determined, Trump's numbers are better than anyone else's. Sure, a sea-change is possible, but no matter how you slice it, Trump has the inertia at double his closest competitor right now. That won't be overcome by wishful thinking.
Further, you need do nothing more than compare number of Trump as opposed to Cruz threads, number of responses, and number of favorable vs. unfavorable posts to see which way the FR winds are blowing.
Finally, there aren't very many FReepers longer-time than myself, and my position is exactly the same as JimRob's, so FR pedigree isn't much of an issue.