What is the relationship between poetic and political order in Walt Whitman's Leaves of Grass?

Be composed—be at ease with me—I am Walt Whitman, liberal and lusty as Nature,
Not till the sun excludes you, do I exclude you,
Not till the waters refuse to glisten for you, and the leaves to rustle for you, do my words refuse to glisten and rustle for you.

How does Leaves of Grass reflect the priorities and beliefs of its 1855 preface? What's the relationship between poetic and political order in Whitman's work?

In the 1855 preface to Leaves of Grass, Walt Whitman looks forward more than to the past and sees the unity of diverse groups as America’s strength. While not completely rejecting old ways, he embraces the vitality of novel approaches, including in the poet’s vision and works. He even equates America to a poem. Whitman strongly promotes the centrality of common people, celebrating their “genius.” These priorities and beliefs can be seen in “Song of Myself” and other poems in the volume.

Whitman states in the preface that “America does not repel the past” and that the country is not overly impatient, understanding that vestiges of the past have “passed into the new life of the new forms.” Politics, caste, and religion are among the earlier forms that influence present and future. It is necessary, however, to cast off the elements that are no longer viable, which had died or become a “corpse.”

The unique blend of different elements is an essential element of America and of creative Americans, especially poets. Whitman calls America “the race of races” as well as “the greatest poem.” He insists that the poet or bard is responsible for seeing new vistas. Like craftsmen and scientists, the poet

sees the solid and beautiful forms of the future where there are now no solid forms.

In “Song of Myself,” Whitman celebrates the diversity of Americans and insists on his connection to all of them and to the past and future. In section 15, he offers a long list of Americans and praises ways they contribute or shape the country. He often remarks on his emotional attachment to them. For example,

The machinist rolls up his sleeves, the policeman travels his beat, the gate-keeper marks who pass,
The young fellow drives the express-wagon.

In section 16, he notes,

I am of old and young, of the foolish as much as the wise, …
One of the Nation of many nations, the smallest the same and the largest the same.