People looking for an explanation for the rise of the Tea Party need to look no further than America’s Scots-Irish heritage, according to Sen. James Webb (D-Va.).

The movement has its roots in the populist-style, bottoms-up democracy that emerged from Scots-Irish migration to America, he said.

“The Tea Party movement is right out of this culture,” Webb observed during a talk Tuesday evening to the Washington Ireland Program at the Dirksen Senate Office Building on Capitol Hill.

Webb, who is retiring after one term in the Senate, is author of Born Fighting, a well-received history of the Scots-Irish and their influence on American culture. A two-hour documentary based on the book premiered in April on the Smithsonian Channel.

During his talk, Webb noted the enduring legacies of the Scots-Irish migration, including country music, fundamentalist values of the Bible Belt and the individualistic nature of some Americans. “They vote on issues of dignity — they don’t vote their pocket book,” he said.

“Karl Rove understands this culture completely,” Webb added. “Democrats don’t even know it exists.”

His audience included Protestant and Catholic university students from Northern Ireland and the Republic of Ireland who are interning at offices in Washington, including on Capitol Hill, the World Bank and the Department of State.

The culture is “tied up with the very fabric of America,” observed John McCavitt, a scholar from Northern Ireland who is writing a biography of Irish-born General Robert Ross, the man who captured Washington during the War of 1812.

Webb served as Secretary of the Navy during the Reagan Administration, and later ran as a Democrat for the Senate, ousting Republican George Allen in 2006. Allen is seeking to reclaim the seat in an election this fall against former Democratic Gov. Timothy M. Kaine.