Rick Santorum is the strongest Presidential candidate in Nebraska- for both the primary and general elections.
Santorum's the top choice of 39% of GOP voters in Nebraska to 25% for Mitt Romney, 16% for Newt Gingrich, and 10% for Ron Paul. Santorum is very popular with Republicans in the state, at a 64/22 favorability rating. None of the other contenders can even hit 50% there, with Romney at 46/39, Gingrich at 38/42, and Paul at 30/52.
As has been the case everywhere he's done well, Santorum's strength is based on support from the most conservative groups of the Republican electorate. He's up 53-18 on Romney with 'very conservative' voters, and also has a 48-18 advantage with Tea Party voters. Nebraska also provides another example of Romney's difficulty connecting with Evangelicals. He's actually up 29-28 with non-Evangelical voters but is still getting crushed overall because of his 50-22 deficit with Evangelicals.
Nebraska's another state where Santorum would gain in a big way if Newt Gingrich got out of the race. His lead would expand to 21 points with him getting 51% to 30% for Romney and 10% for Paul.
Santorum's the strongest candidate in the general election in Nebraska as well. He leads Barack Obama by 17 points at 55-38. The other Republicans lead by smaller, but still healthy, margins. Romney and Paul are each up by 12 at 51-39 and 49-37 respectively. Gingrich is the weakest of the GOP hopefuls, leading Obama by 9 points at 49-40.