CHARLOTTE – They range from precinct leaders to sitting governors, but delegates share a common cause – unifying and moving their political party forward.

Delegates are most known for cheering, waving signs and showing solidarity for candidates on the floors of political conventions, but their roles start long before their party's big event.

Robert Hillman, a 2012 Democratic Party delegate, is in a unique position as his party's national convention is coming to his backyard.

"I feel, to some degree, I'm somewhat of an ambassador for Charlotte," he said.

In 2008, Hillman was a field organizer in Charlotte for then Sen. Barack Obama. In 2012, he'll cast a vote in Charlotte as a delegate to officially nominate the president for a second term.

“This is just one other vote that I get to cast to put me in the center of history,” said Hillman.

Hillman is one of more than 4,000 Democratic Party delegates, a group that includes 172 from North Carolina. More than 3,200 delegates are chosen to represent their party by fellow members at the local level and another roughly 800 elected officials and other party leaders are deemed superdelegates.

Since Charlotte is hosting the convention, more than 200 people applied to be one of the three men or three women representing the Ninth District.

“People came out of everywhere to become a delegate, so we had to have multiple rounds, I think it was either seven or eight rounds of voting to whittle the crowd down,” Hillman said.

Hillman and other delegates are required on the floor during the convention's afternoon sessions to cast votes on official party matters as well as approving the Democrats' platform for the next four years.

“Being in this process is important to me from the perspective of participating in the democratic process,” said Hillman.

For first time Republican delegate Matthew Ridenhour, serving his party at the national convention is the fulfillment of a lifelong dream.

“I actually asked my mom, 'How do you become a delegate or go to these big conventions,' and she said, 'Well, you stay active, maybe one day you can actually be a delegate,'” he said. “I didn’t actually expect it to ever happen, but here I am.

Ridenhour is one of 55 Republican delegates who will represent North Carolina in Tampa. There are nearly 2,300 total GOP delegates nationally. Unlike the Democrats, who have an incumbent president, Republican delegates this year might cast votes for other candidates.

Ridenhour will cast his official presidential delegate vote not for Mitt Romney but Ron Paul because delegates from each state must vote in equal proportion to how the state voted for president.

“A lot of people think, 'Well, the GOP nominee has already been chosen,' technically not until the convention is concluded has the nominee actually been selected,” Ridenhour said.

Local Republican and Democratic party delegates are selected in a presidential election year They'll be chosen again in early 2016 in congressional districts across the country.