A year and a half from now the next presidential contest will kick into high gear, as the Iowa caucuses get underway. Those caucuses are important in deciding who will be the nominee of each party. While the winner in Iowa won't necessarily be the party's nominee, it will certainly show which candidates don't have any chance of getting the nomination. That's why I found this Public Policy Polling survey (taken between May 15th and 19th of 914 Iowa voters, with a 3.2 point margin of error) interesting. The survey contained 356 Democrats (with a 5.2 point margin of error, and 303 Republicans (with a 5.6 point margin of error). The rest were Independents.
As you can see, the Iowa Republicans prefer their candidate to be more extreme than some other states -- with Huckabee and Cruz leading the field (over slightly more moderate candidates like Bush and Christie). No candidate has a commanding lead, but this does show it's going to be hard for the party to nominate a candidate moderate enough to appeal to a majority of Americans.
The Democratic preference was no surprise. As in other states, Hillary Clinton has a commanding lead. The only way anyone else can be nominated, in my opinion, is for Hillary to decide she won't run (and I don't think that'll happen).
The survey also questioned all respondents (Republicans, Democrats, and Independents) on who they would vote for in a general election -- matching Hillary Clinton against the top GOP candidates. And right now, Hillary would win against any of them (see chart below).