“A republic, if you can keep it.”

Bright Lights, Big City (1984)

Last Speech to the National Convention (26 July 1794)

President's weekly address (6 June 2009) https://www.whitehouse.gov/the_press_office/WEEKLY-ADDRESS-President-Obama-Outlines-Goals-for-Health-Care-Reform/
2009

1961, Address to ANPA
Context: Without debate, without criticism, no Administration and no country can succeed — and no republic can survive. That is why the Athenian lawmaker Solon decreed it a crime for any citizen to shrink from controversy. And that is why our press was protected by the First Amendment — the only business in America specifically protected by the Constitution- -not primarily to amuse and entertain, not to emphasize the trivial and the sentimental, not to simply "give the public what it wants" — but to inform, to arouse, to reflect, to state our dangers and our opportunities, to indicate our crises and our choices, to lead, mold, educate and sometimes even anger public opinion.
This means greater coverage and analysis of international news — for it is no longer far away and foreign but close at hand and local. It means greater attention to improved understanding of the news as well as improved transmission. And it means, finally, that government at all levels, must meet its obligation to provide you with the fullest possible information outside the narrowest limits of national security — and we intend to do it.

Source: The Da Vinci Code

Source: Rocky Balboa

There is no evidence that Franklin ever actually said or wrote this, but it's remarkably similar a quote often attributed, without proper sourcing, to Alexis de Tocqueville and Alexander Fraser Tytler:
:A democracy cannot exist as a permanent form of government. It can only exist until the majority discovers it can vote itself largess out of the public treasury. After that, the majority always votes for the candidate promising the most benefits with the result the democracy collapses because of the loose fiscal policy ensuing, always to be followed by a dictatorship, then a monarchy.
Misattributed

Source: Devil in Winter