Romanticism, unlike the other "isms", isn't directly political. It is more intellectual. The term itself was coined in the 1840s, in England, but the movement had been around since the late 18th century, primarily in Literature and Arts. In England, Wordsworth, Shelley, Keats, and Byron typified Romanticism. In France, the movement was led by men like Victor Hugo, who wrote the Hunchback of Notre Dame. Although it knew no national boundaries, Romanticism was especially prevalent in Germany, spearheaded by artists like Goethe and thinkers such as Hegel.
The basic idea in Romanticism is that reason cannot explain everything. In reaction to the cult of rationality that was the Enlightenment, Romantics searched for deeper, often subconscious appeals. This led the Romantics to view things with a different spin than the Enlightenment thinkers. For example, the Enlightenment thinkers condemned the Middle Ages as "Dark Ages", a period of ignorance and irrationality. The Romantics, on the other hand, idealized the Middle Ages as a time of spiritual depth and adventure. Looking wistfully back to the Middle Ages, the Romantic influence led to a Gothic Revival in architecture in the 1830s. Gothic novels increased in popularity, and in art, paintings of various historical periods and exotic places came into vogue.
It would be impossible to cover all of the Romantics in such a short space (and a disservice to them to attempt it), but representative examples can be given. Mary Shelley (the wife of Percy Bysshe Shelley, published Frankenstein in 1818. Few would argue that it is the best work of the British Romantics, but it is indicative. In this story, a scientist is able to master life, animating an artificially constructed person. But this "miracle of science," far from a simple story of man mastering nature through reason, ends up having monstrous results.
In Germany art, Friedrich Schiller produced plays known for their sense of a German "Volk", or national spirit. Karl Friedrich Schinckel led the Gothic Revival movement, beginning his first plans for Gothic structures as early as the 1820s. German romantic philosophy was dominated by W.G.F. Hegel. He construed the development of the state as part of a historical process, or "teleology". He is particularly famous for outlining a concept of the dialectic: the mind makes progress by creating opposites, which are then combined in a synthesis. Hegel tied his philosophy into nationalism by arguing for a German national dialectic that would result in synthesis into a state. Hegel's work increased the emphasis people put on historical studies, and German history writing boomed. Partially as a result of Hegel's influence, the idea developed that Germany's role was to act as a counterbalance to France. Seeing themselves as such, Germans began to feel that liberalism was not appropriate in Germany.
The French had their Romantics too, though not in the same profusion as Germany. For instance, Romantic painting is always associated with Eugene Delacroix, who prized the emotional impact of color over the representational accuracy of line and careful design. Delacroix painted historical scenes, such as "liberty Leading the People" (1830) which glorified the beautiful spectacle of revolution, perhaps construing it as part of the French national character. After 1848, Romanticism fell into decline.
Romanticism can be construed as an opposite to "classicism," drawing on Rousseau's notion of the goodness of the natural. Romanticism holds that pure logic is insufficient to answer all questions. Despite a founding French influence, Romanticism was most widespread in Germany and England, largely as a reaction to the French Enlightenment. It also was a response to French cultural domination, particularly during the Napoleonic Wars. The Romanticist emphasis on individualism and self-expression deeply impacted American thinking, especially the transcendentalism of Emerson.
Instead of labeling, classifying, listing, tallying and condemning, the Romantics were relativist. That is, they looked less for ultimate, absolute truth than did Enlightenment thinkers. Romantics tended to think that everything had its own value, an "inner genius". Even in morality, the Romantics began to question the notion that there even was such a thing as absolute good and evil. Instead, each society was seen to create its own standards of morality. Romanticism also fueled many "isms" with the basic idea that "genius" had the power to change the world. German Romanticism, with its idea of a Volksgeist unique to each nation (derived from Herder's writings), gave an intellectual basis to nationalism.
The movement of Romanticism encompasses several contradictory aspects: several ideas are grouped into the movement, and they do not always fit together. For instance, some Romantics utilized the ideology to argue for the overthrow of old institutions, while others used it to uphold historical institutions, claiming that tradition revealed the "inner genius" of a people. Basically, as long as romantic intellectual passion, not rationalism and strict reason, were the basic underpinning of an idea, than it can be classified as "Romantic."
Interestingly, because of its geographical distribution, some historians argue that Romanticism was the secular continuation of the Protestant Reformation. Romanticism was most prominent in highly Protestant countries like Germany, England, and the United States. France, which had a significant Protestant movement but which remained Catholic-dominated, had something less of a Romantic movement. Other solidly Catholic countries were even less impacted by Romanticism.