Mr. Grayson, who lost a bid for the Republican Senate nomination in Kentucky to Mr. Paul’s son Rand, said he did not believe that Mr. Paul would win the nomination. But he said the Tea Party energy “is going to be very helpful, especially in a caucus state like Iowa, where it doesn’t take many votes” to win.

In the 2008 campaign, Mr. Paul’s message of fiscal discipline, harsh spending cuts and dire warnings about the deficit seemed out of sync with the relative affluence through most of 2007. Now, the debate consuming Washington is about the issues that Mr. Paul cares about: the debt, the deficit and the consequences of failing to shrink the size of government.

Drew Ivers, a member of the state central committee of Iowa’s Republican Party and the chairman of Mr. Paul’s Iowa leadership team, is convinced that this year could be different.

“Ron Paul finds himself right in the epicenter of the three or four or five of the most critical and controversial issues in our nation today. The spending. The war. The financial crisis,” Mr. Ivers said in an interview Tuesday. “That’s how snowballs develop, you know. They start small, and they get bigger as they roll downhill.”

During the 2008 campaign, Mr. Paul proved to be a better-than-expected fund-raiser, but he did it late in the game. In December 2007, just days before the Iowa caucus, Mr. Paul raised $6 million in a one-day “money bomb” that was timed to coincide with the 234th anniversary of the Boston Tea Party. This year, Mr. Paul would most likely tap into his donor base much earlier, giving him the opportunity to advertise on television throughout the primary season.

He could also be helped by less competition for donor dollars than in 2007, when he was competing against a field of a dozen Republican candidates, including several with deep pockets or a proven ability to raise millions.

Mr. Paul also won’t have to spend so much time in this campaign explaining who he is and what he believes. When he started his bid for the Republican nomination in January 2007, he was a little-known member of Congress. A Washington Post poll in February 2007 put him at just 1 percent, if the vote were conducted then. Four years later, Mr. Paul’s poll numbers remain low, but his participation in the 2008 debates and his frequent appearances on television have kept him in the news.