Ron Paul is refusing to concede Maine. He was expecting to win caucuses that were canceled due to snow. The Republican Party of Maine then announced that those caucuses would not matter:

But in Washington County, where Paul had expected to perform well, the caucus was postponed until Feb. 18 due to an expected snowstorm. Washington County Republican Chairman Chris Gardner told the AP he had no idea when the caucuses were postponed that his county would no longer count toward the grand total.

And Rick Santorum says Mitt Romney paid to win the CPAC straw poll:

Romney beat Santorum by 7 points Saturday in a straw poll of almost 3,500 attendees at the Conservative Political Action Conference (CPAC). Santorum pointed out that Ron Paul had won the poll in both of the past two years "because he just trucks in a lot of people pays for their ticket, they come in and vote and then leave."

Did Mitt Romney buy CPAC? Did the Republican Party manipulate the results in Maine so that they'd land in Mitt Romney's favor? Probably and maybe, in that order. But that's the thing about running for president: If you cheat and you win, you're still the president. Very occasionally, you get caught. But if your opponents waste their time complaining about fair play, that gives you time to seize a valuable lead.