The recent polls are pretty unanimous that there's a three-way tie going into tomorrow's Iowa presidential caucus, with Mitt Romney, Ron Paul, and Rick Santorum all drawing support from about 20 percent, give or take, of likely caucus goer. But this is a caucus, not a primary, so that's not likely how Iowa's delegates will be distributed.
Once neighbors gather by precinct and start talking to each other, they'll quickly realize which candidate has the most votes, and it's quite likely that some voters will strategically switch allegiances to their second or third choice. Each precinct sends delegates to their county convention, where the process is repeated onto the district convention, and ultimately to the state convention, where the national delegate selection actually takes place. Delegates are unbound at all stages of the process.
So it's quite possible that, say, Rick Santorum could prevail tomorrow, and by a surprisingly large margin, as he garners support from Michele Bachmann supporters and other anti-Romney voters, yet Romney could ultimately earn the bulk of Iowa's delegates if he wraps up the nomination prior to the state convention, and Republicans fall in line behind the national standard bearer.
Just something to keep in mind if the caucus results don't quite match the final polls.