Political privacy has been a concern since voting systems emerged in ancient times. The "secret ballot" is the simplest and most widespread measure to ensure that political views are not known to anyone other than s/he voting - it is nearly universal in modern democracy, and considered a basic right of citizenship. In fact even where other rights of privacy do not exist, this type of privacy very often does.
Because politics is fundamentally about settling disputes of when to apply violence and violent restraint, and appointing officials to hold a monopoly on violence, it puts winners and losers in unique positions to revenge themselves on each other. In a democracy, the winner is vulnerable as s/he often appears in public to explain policies and gain additional support. The loser is also vulnerable as s/he is subject to the interpretation of criminal justice by winners - law enforcement is often very prejudicial, and an independent judiciary is not always available to ensure fairness in how winners of a political conflict deal with losers. Uncertainty about who supported what measure, and the right to keep one's opinion to oneself and not be required to reveal it except voluntarily (by joining a political party or answering opinion polls), aren't generally challenged even by the most strident national security advocates. In this sense, supporters and detractors of the state have a common position: when operating within the existing legal bounds of a political system, opinions should be measured only in aggregate.
A jury also typically provides its opinion only as an aggregate and jurors have the right not to reveal whether they found someone 'guilty' in cases where a unanimous verdict is not required. When found 'not guilty', it is also not revealed who opposed or advocated a 'guilty' verdict - particularly important as the accused will now be set free and might be tempted to seek revenge against those who disbelieved him.
Ballot secrecy however is not typically part of legislative procedure, as in a representative democracy the votes of each legislator are supposed to be literally 'representative' of constituents' views and political party positions - if these are in conflict then that too must be observed by the voters and parties. Representative recall measures further discipline this by permitting voters to 'fire' their representative during a legislative session. Chairs of committees in a legislature may be determined by open vote or by secret ballot, if there are concerns that retribution may apply to a legislator from some particularly powerful central figure advocating a specific candidate:
In Canada in 2002 the ruling Liberal Party of Canada under Prime Minister Jean Chrétien opposed a successful measure by Paul Martin Jr, also a Liberal and widely regarded as Chretien's rival or successor, to require Canadian House of Commons committees to choose chairs by secret ballot. The public debate centered on the issue of whether representatives must do public business in public, or whether the Prime Minister's Office was overly directing that business to a degree unintended by the Canadian Constitution or traditions in a parliamentary democracy. Martin's faction carried the day with support from opposition parties, and many breakaway Liberals who resented their relatively weak power related to that of their Leader - and thus wanted the power to select chairs that he did not approve of, without being clearly identified and thus subject to his retaliation.
Outside legislatures, the political privacy of ordinary citizens has always been an issue. Representatives are supposed to serve citizens equally without regard to how they voted in the most recent election - this would seem to be impossible if it is easy to look up their vote. In another case in Canada in early 2002, an Ontario federal Liberal MP wrote an ill-advised letter to a constituent telling him that if he wished help on some matter he'd written to the MP about, next time he "had better vote Liberal." Apparently, the MP's office had access to a canvasser's list of the riding and had noted the man's name as having a lawn sign for a competing candidate during the most recent election. A cynical view is that this is normal behavior for all representatives and that denying opponents favors they grant to supporters is just part of the "spoils of victory".
Political privacy concerns extend far beyond dealings with voting and legislative systems, however. Citizens' opinions on almost anything can be taken as having political implications. For instance, someone opposing legal recognition of homosexual marriage might well be considered homophobic or opposed to legal equality for gays and lesbians - even if his or her objection is procedural or economic. For these reasons, opinion pollsters stringently protect respondents' privacy, in order to more accurately gauge their real political temper.
Radical or extreme political opinions that do not achieve expression to a satisfactory degree within a formal electoral system or legal system present a special problem: while all of the above concerns remain, they must be balanced against the concern that the system itself will be directly and violently opposed by those of such views, relatively disadvantaging those who work within the system for change.
A typical issue of this sort is the wearing of masks during protests and demonstrations, e.g. in the anti-globalization movement. The hiding of identity as radical views are expressed, e.g. favoring some form of anarchism, has long been considered a fundamental right:
Although technically this is a disguise, and demonstrators often break one or more laws during a protest or blockade, historically there has been broad tolerance of the right to express such political views without necessarily being subject to legal or social retribution. To a degree, this recognizes the need for some means of "blowing off steam", or the system itself demonstrating its power and confidence by choosing restraint. Many nations, however, have now passed laws against masks in protest and demonstration contexts, despite the fact that police in such circumstances very often appear masked and without badge numbers.
Most privacy advocates view such measures as typical of a carceral state - where the state itself knows everything, and there is neither political nor consumer privacy nor even much medical privacy - a special concern is the gathering of biometrics. This may enable identity theft by the state itself, framing citizens whose political views it finds offensive.
The more political privacy is violated, the easier it becomes to frame an innocent person using credible-sounding variations of their views and fabricated recordings. In 2001-2003 these concerns became relevant on the global diplomatic scene, as the reputed capture of recordings of Usama bin Laden boasting about the September 11, 2001, terrorist attacks, and reputed intercepts of Iraqi Republican Guard officers conspiring to hide evidence of weapons of mass destruction from United Nations weapons inspectors, was challenged, especially in the Muslim world and especially Iraq, as being "well within the capabilities of the CIA to fabricate."
Credibility of anything other than firsthand evidence being difficult to establish, but motivations for believing hearsay and evidence 'found' without firsthand corroboration from those who were actually there, not to mention probability of torture being used in gaining confessions or other 'intelligence', makes it all but impossible to rule out the conspiracy theories. Accordingly like many political matters it boils down to a question of who is ultimately trustworthy.
Within the United States itself, political privacy of citizens has come into open question, with the government having prepared so-called No-fly lists of individuals with no history of advocating violence or hijacking, but who strongly opposed the Bush Administration and its ideology. While few individuals were detained for long, many were denied access to flights and thus economic or political opportunities, including prominent members of the Green Party of the United States, a wholly peaceful organization with no ties to terrorism.
It is such political harassment and overt singling-out of persons with unpopular views that tends to characterize the first stages of any police state. Accordingly, civil rights advocates have little patience for the excuse that these measures "ultimately protect" the citizen. Political privacy may be more of a concern in the future as the capacities of persuasion technology improve, enabling pitches to be tailored to appeal to one's most fundamental personal beliefs - with or without human labour - making telemarketing scams easier, and making it extremely easy to slant opinion polls to get a desired result. It may also become harder to defend political privacy, e.g. which articles of the Wikipedia one has authored or edited, where extreme views and strong challenges to the dominant political system are beginning to threaten the power of dominant cliques in society - who tend to prefer in general a zero-accountability carceral state.
One response to the issue of political privacy as such is that since politics is ultimately about violence, and violence ultimately about other people, any political privacy outside the expression of voting is inappropriate. Bernard Crick, for instance, a notable advocate of politics as the necessarily-public form of ethics, defined politics itself as "resolution of moral conflict, or ethics, in public". From this point of view, one may have no right to political privacy, and even such measures as a secret ballot may be denied based on the grounds that political differences between neighbors or friends must be open, in order to avoid over-empowering some central authority.
Fear of such a central authority, that argument goes, is the problem, and knowing there is no political privacy, people become maximally motivated to ensure that the central authority has no arbitrary power. Junius said that "the subject who is truly loyal to the chief magistrate will neither advise, nor consent to, arbitrary measures." Knowing that such measures might be directed against oneself may be the strongest possible motivation to avoid advising them against others.
Finally, there is the issue of anonymous authorship of opinions. The Federalist Papers that in part sparked the American Revolution were written anonymously and pseudonymously. Most peer reviewed journals employ anonymous reviewers - and some publish only unattributed views, e.g. The Economist. From classic to modern times, anonymity has proven an effective counter to groupthink - ossified mind-sets that very often become politically dangerous.
This Wikipedia article, for instance, was written anonymously, and the author insists on such authorship in part to protect other authors who may also choose anonymous authorship for more controversial views. The more who author anonymously and "neither confirm nor deny" their authorship, this argument goes, the harder it is to confirm identity, and therefore the harder to intrude into anyone's political privacy.
Mainstream views in North America tend to weakly support this view, in contrast to very strong support for it by its nations' founders: Benjamin Franklin said that "those who give up a little liberty to gain a little security, deserve neither." Political liberties being to a degree dependent on basic rights of political privacy and expression of views without retribution, this could be applied to modern contexts to argue strongly against such measures as Total Information Awareness. Knowing the political views of the citizen and what s/he has done to oppose the state and its law enforcement, how can an administration or police officer actually behave in a neutral way?
The answer, in modern democracies, is that this is neither a function of the elected administration nor the lower-level legislators nor the police, but is solely in the hands of the independent judiciary - who are supposed to be neutral and appointed by prior administrations of all political views, and well beyond reach of political influence.
See also: legal privacy, client confidentiality, medical privacy