Yes, Ronald Reagan was a harbinger of the Tea Party, because he understood that the government that governs least, governs best. In his closing speech Reagan was proud of the fact that he had starved the government to make it smaller. He cut taxes. These are all things the Tea Party stands for.
It is often said that Ronald Reagan would not recognize the current Republican Party, but that is probably a factor of the times he lived in rather than his core beliefs. One of Reagan's most famous sayings is, "The nine most terrifying words in the English language are: 'I'm from the government and I'm here to help.'" That statement is the epitome of what the Tea Party believes.
Reagan's tax policy and his wish for a small federal government might seem to align with the tea party. However, Reagan's foreign policy set him firmly apart from the tea party. Reagan's firm wish for the fall of the Berlin wall and for the end of the Soviet oppression in Eastern Europe. The tea party is a much more isolationist. Reagan was also much more willing to negotiate than the tea party is.
I do not believe Ronald Raegan was a harbinger of the Tea Party. I can see where people would draw that conclusion but I feel it is entirely different. Raegan was unique because people thought there was probably someone behind him that was in control. This isn't the case with the Tea Party.
Ronald Reagan was the 21st centuries Teddy Roosevelt. He was an amazing speaker he had a clear place he wanted the country to go and he made sure that nothing was in the way for the country to get there. His ideals were different from the tea party in that he never real talked about the de-liberalization of the government because that didn't exist while he was president.