"Discussion of public issues and debate on the qualifications of candidates are integral to the operation of the system of government established by our Constitution. The First Amendment affords the broadest protection to such political expression in order "to assure [the] unfettered interchange of ideas for the bringing about of political and social changes desired by the people." Roth v. United States, 354 U. S. 476, 354 U. S. 484 (1957). Although First Amendment protections are not confined to "the exposition of ideas," Winters v. New York, 333 U. S. 507, 333 U. S. 510 (1948), "there is practically universal agreement that a major purpose of that Amendment was to protect the free discussion of governmental affairs, . . . of course includ[ing] discussions of candidates. . . ." Mills v. Alabama, 384 U. S. 214, 384 U. S. 218 (1966). This no more than reflects our "profound national commitment to the principle that debate on public issues should be uninhibited, robust, and wide-open," New York Times Co. v. Sullivan, 376 U. S. 254, 376 U. S. 270 (1964). In a republic where the people are sovereign, the ability of the citizenry to make informed choices among candidates for office is essential, for the identities of those who are elected will inevitably shape the course that we follow as a nation. As the Court observed in Monitor Patriot Co. v. Roy, 401 U. S. 265, 401 U. S. 272 (1971), "it can hardly be doubted that the constitutional guarantee has its fullest and most urgent application precisely to the conduct of campaigns for political office." The First Amendment protects political association as well as political expression. The constitutional right of association explicated in NAACP v. Alabama, 357 U. S. 449, 357 U. S. 460 (1958), stemmed from the Court's recognition that "[e]ffective advocacy of both public and private points of view, particularly controversial ones, is undeniably enhanced by group association." Subsequent decisions have made clear that the First and Fourteenth Amendments guarantee "freedom to associate with others for the common advancement of political beliefs and ideas,'" a freedom that encompasses "`[t]he right to associate with the political party of one's choice.'" Kusper v. Pontikes, 414 U. S. 51, 414 U. S. 56, 414 U. S. 57 (1973), quoted in Cousins v. Wigoda, 419 U. S. 477, 419 U. S. 487 (1975)."