As far as "Deus Caritas Est" is concerned, I'd suggest a particularly Tocquevillian influence may be found in Paragraph 28. Here, Pope Benedict underlines the folly of allowing the state to absorb all social activity and letting it evolve into an all-encompassing bureaucracy that is incapable of discerning people's deeper moral and spiritual needs.
In "Democracy in America," Tocqueville suggested that democracies were especially susceptible to this temptation and could develop the characteristics of what is called soft despotism.
This despotism, Tocqueville argued, was one in which the democratic state slowly but surely suffocated all the independent and spontaneous initiatives arising from that complex of free associations we often call "civil society" -- associations that are, in most situations, far more effective in addressing people's problems than bureaucracies.
But the real challenge posed by the encyclical to Christians is to ensure that Christians' charitable work remains unashamedly Christian. This means, as the encyclical stresses, that it can never be allowed to develop into mere political activism.
Politics, for Catholics, ultimately concerns the common good, but it can't encompass the whole of the common good and we all know of instances when political activity has done enormous harm to the common good.
An associated challenge identified by "Deus Caritas Est" is the perennial temptation for Christian charitable work to become secularized in its motivations and methods.
That's why Pope Benedict emphasizes that Christian charities must be "credible witnesses to Christ."
On a practical level, this accent on being manifestly Christian means that Christian charities cannot act in ways that contradict the Truth revealed by Jesus Christ and imparted to the world by his Church.
This is a lesson we in America once understood, but have forgotten in recent decades. The government cannot be the solution to all problems, lest it remove all initiative from the people.