In essence the gentry and urban elites were the individuals that led the American colonists into and through the Revolution. They then developed the government that is still in existence today in the United States; the Constitution. The American Revolution and creation of the US Constitution, while they are both considered to be victories of the masses it was the well-to-do that got everyone involved in wanting independence and ratifying the government.
The gentry leaders (or landed, family plantation farmers) were persons such as Thomas Jefferson, George Washington, Henry Laurens, etc. These were educated, wealthy individuals; plantation owners and slave holders.
The urban elites were persons from the larger towns or cities. Men such as Samuel Adams, Alexander Hamilton and Benjamin Franklin. These were educated persons that gained wealth as merchants or business owners.
Then there are individuals such as John Adams that transcend both arenas. He was a Massachusetts farmer and an urban-ite; well educated and wealthy.
Together the gentry and urban elites developed American politics.It is from these persons that the recognition of the strong arm of power can become unruly, over powering if it is not limited. As a result the birth of what is considered modern day representative government occurs with the checks and balance system. These two fundamental beliefs took root in what these men put into action.
What is interesting is that the vast majority of these leaders truly believed in the fact that the the educated, wealthy gentry and urban elites were born to be the leaders. Yet they knew they could not lead without involving the uneducated, hard working masses. During this era there were larger numbers of slave and/or indentured workers. One would easily theorize this for the deep south but it also existed in the urban areas as well. (The very best book, most in depth account on this topic is The Urban Crucible: The Northern seaports and the Origins of the American Revolution by Gary B. Nash.) For example, in New York City and Philadelphia, by the mid-1740's it is estimated that 2 out of every 5 laborers were slave or indentured. The bottom line was that the pre-revolutionary economy and socio-economic structure was one in which the top 10% of the people were the economic elite and they were empowered. However, as Nash states, they sought in America a "Moral Economy." From this perspective American politics developed into those who wanted separation from the crown known as Whigs or Patriots or those wanted to continue down the path of loyal English subjects known as Tories or Loyalists. During the Constitutional era there will be Federalist and Anti-Federalists factions and later yet in the 1790's the Republicans and the Federalists. Therefore, one can make the argument that the birth of American Politics comes from the gentry and urban elites in the 18th century.