Republican presidential candidate Rep. Ron Paul speaks at the university in Chico, Calif. (Frank Rebelo, CSU-Chico/AP)

Republican presidential candidate Ron Paul's hard-nosed troops aren't giving up. Far from it. As demonstrated anew last weekend in Nevada and Maine, they are shaking up the GOP establishment and causing discomfort to strategists for front-runner Mitt Romney by capturing delegate blocs at the state level as they prepare for the Republican National Convention in Tampa this summer.

Paul organizers won't tell the media exactly what they will do in Tampa or which states they will target next. And they have many challenges. For example, party rules often require national delegates to support the winner of state-level contests on the first ballot. So even though newly selected delegates in Nevada, Maine and elsewhere might personally back Paul, they could be bound to vote for Romney on the initial roll-call vote. But there is an alternative scenario. Paul strategists tell me that a delegate is permitted to abstain on the first ballot, which could conceivably deny Romney the nomination if enough of them go that route, combined with those still committed to candidates who have dropped out.

There is a strong desire among Paul supporters at the grass roots to push as hard as they can to put his name formally into nomination. They want him to address the convention in prime time and make his libertarian case directly to the nation. They also want to exert an influence on the party platform.

One tactic is for Paul cadres to win majorities in five state delegations, which under party rules would entitle Paul to have himself nominated, Paul campaign leaders say. Many Paul supporters don't believe Romney is conservative or reliable enough to carry their banner.

"Our movement is at fever pitch," a senior Paul adviser tells me. "Our movement is organic."

There is the potential for considerable embarrassment for Romney. If Paul managed to win a speaking slot, he might come across as a divisive force and illustrate how far Romney has to go to unify the GOP. If he doesn't get a speaking slot, Paul supporters might feel cheated and would be so incensed that they wouldn't turn out for Romney in the fall election, Paul strategists say.

Even though Paul has failed to win the popular vote in any state contest, his supporters are mastering party rules at the state level and in some cases are outmaneuvering Romney backers in gaining delegates.

Paul forces took over the Nevada Republican state convention last weekend and captured 22 of the 25 delegates at stake even though Romney won the Nevada caucuses in February with 50 percent of the vote to Paul's 19 percent.

Paul also dominated the Maine GOP convention last weekend, costing Romney another 11 delegates despite Romney's earlier victory in the Maine popular vote, party leaders say.

Romney still has 856 delegates, 288 short of the 1,144 needed for the nomination, according to an Associated Press count. Former Sen. Rick Santorum of Pennsylvania has 257 and former House Speaker Newt Gingrich has 130. Both Santorum and Gingrich have dropped out of the race. Paul, a U.S. representative from Texas, has 94.