What were the reasons for political realignment in the 1830s and the emergence of the Whigs.

If the question refers to the US Whig party, the political realignment followed the rise of Andrew Jackson and his dominance of the national political scene with his spoils system and centralization of power. Former Federalists, National Republicans and those simply opposed to Jackson combined as the Whig party to push for a stronger Congress, internal improvements and support for business interests. The Whigs ran regional presidential candidates in 1836 and had its firs national convention in 1839.