TAMPA, Fla. >> The future of what Ron Paul started rests with supporters like Ashley Ryan, who will attend Paul’s final presidential campaign rally here with decidedly mixed feelings.

Ryan, a 21-year-old college student, will take over as Maine’s national committeewoman after sitting as a Paul delegate at this week’s Republican National Convention. But in a credentials dispute, hard-bargaining party leaders left Paul forces with only half the Maine delegates they thought they had won this year — a blunt reminder of Mitt Romney’s grip on the proceedings.

“It was a huge slap in the face,” Ryan complained. Though her unseated Maine colleagues can attend with guest passes furnished by the Iowa delegation, she said, “I was very disappointed.”

Yet Paul’s supporters can celebrate achievements that an earlier generation of libertarians never tasted. Despite Tropical Storm Isaac, Paul is still scheduled to stage a valedictory rally on Sunday before an estimated 10,000 supporters at the University of South Florida’s Sun Dome. Its speakers, including Ryan, were planning to send the Republican Party a message about their commitment to grow in influence as the 77-year-old Paul moves on.

The libertarian movement has always boasted intellectual champions. But it has gotten something new from Paul, the iconoclastic veteran House member from Texas, whose small-government, low-tax, noninterventionist views found new attention in the Tea Party era and served as the focus of a determined grass-roots effort to shake up the Republican establishment.

Over three separate presidential bids, Paul has given libertarians a leader from the world of electoral politics, a beachhead within the party, and a passionate if disparate army of activists. The onetime obstetrician has even bequeathed the movement a successor: his son, Sen. Rand Paul of Kentucky.

“We used to say most people found libertarianism by reading Ayn Rand,” said David Boaz of the Cato Institute, a libertarian research organization in Washington. “In the last five years, most people have found libertarianism by listening to Ron Paul.”

Brian Doherty, an editor at Reason magazine and a historian of the libertarian tradition, goes so far as to call the Texas Republican “a miracle.” Before Paul, the movement found much to admire in political figures like Barry Goldwater and Ronald Reagan — but also big disappointments.

Even now, backers like Ryan see the Paul campaign ending in a fizzle rather than a bang at the convention. In addition to disappointments over delegates, Paul, who finished second to Romney in New Hampshire’s signature primary, will not get to address the party convention.

That reflects both sides of the movement’s new circumstances. To enhance its long-term viability among Republicans, Paul campaign leaders decided to cooperate with Romney forces for a smooth convention, while eschewing compromises that would have alienated core supporters even more.

Paul, in an interview, said convention planners had offered him an opportunity to speak under two conditions: that he deliver remarks vetted by the Romney campaign, and that he give a full-fledged endorsement of Romney. He declined.

“It wouldn’t be my speech,” Paul said. “That would undo everything I’ve done in the last 30 years. I don’t fully endorse him for president.”

Paul’s campaign chairman, Jesse Benton, acknowledged the frustrations that the Paul high command had been forced to manage.

Some true believers want to “dress in black, stand on a hill and say, ‘Smash the state,”’ said Benton, who is married to one of Paul’s granddaughters. But “it’s not our desire to have floor demonstrations. That would cost us a lot more than it would get us.”

Just eight years ago, “it was fringy people in the John Birch Society” who were espousing Paul’s ideas for taking on the Federal Reserve system, Benton said. “Now it’s the Republican Party” that has drafted a platform plank calling for auditing the central bank.

The purity of the movement’s principles has long left it in a form of self-imposed isolation. The minimalist role it envisions for government repels the vast majority of Democrats; its noninterventionist foreign policy and live-and-let-live social views repel most Republicans.

The Pew Research Center’s most recent study of groups within the electorate, in 2011, categorized 10 percent of registered voters as libertarians. But even that relatively small group, said the center’s president, Andrew Kohut, held more moderate views on the role of government and foreign affairs than Paul’s.

Still, Paul has managed to expand the movement’s ranks. The 2 million votes he received in this year’s Republican nominating contests were nearly five times the number he received as the Libertarian Party’s presidential nominee in 1988.

He largely credits fortunate timing. The 2008 financial crisis and growing fatigue with the wars in Iraq and Afghanistan made some voters more receptive to his message on monetary and military policies.

“There’s a lot of luck in politics,” he said.

Simple generational change could give the movement a boost in elections to come. Younger voters of all stripes display increasing tolerance on social issues like same-sex marriage; the fiscal conservatives among them will fit into the libertarian camp far more easily than older, conservative Christian Republicans.

In New Hampshire, for instance, Paul drew half his votes from people younger than 45. Three-fourths of Romney’s votes came from those 45 and older.

Doherty, the author of a history of libertarianism called “Radicals for Capitalism,” credited Paul with “normalizing” a movement once derided as kooky. But he said the movement must remain aggressive in order to grow more rapidly and avoid being taken for granted the way, in his view, Republicans have taken for granted the religious right.

“It can’t be growth just by age attrition,” he said. “The young people have to start connecting with the older people.”

A further challenge is expanding the movement’s support among women, who tend to express higher support for activist government than men do. The most promising avenue, Benton said, may be the anti-war stance that Paul has articulated, which might also attract more Republican men on the basis of fiscal conservatism as the nation’s debt burden grows.

Balancing pragmatism and principle could prove tricky for Rand Paul, who Boaz said “sees himself as a potential presidential nominee.”

Rand Paul has shown a greater commitment than his father to operating within Republican Party institutions. The foremost recent example: in June, Paul gave Romney the endorsement that his father would not. He is scheduled to address the convention on Monday.

“There were a lot of people who were upset” at the endorsement, said Ryan, the youthful Maine delegate. “Rand’s going to have a lot of work ahead of him to secure his base if he wants to be the next liberty candidate.”