The problems with many of these, is that a lot of obviously authoritarian governments like to pretend they're doing just fine. Note that I'm not arguing the US is yet an authoritarian police state, or that many of these apply to the US, but rather that it is also not helpful to make the criteria too strict - a key feature of many authoritarian governments is that they try to superficially appear, at least to their supporters who may especially in early phases make up a substantial proportion of the population, as "gentler" and more open than they are.

> When it becomes illegal to oppose the current government?

DDR on paper was a multi-party democracy. It was legal to oppose the current government. Even take part in parties other than the socialist party. Just if you did, Stasi might invent other ways of making you shut up, or you'd run afoul of other laws.

Of course the other parties all took part in a single electoral block with the SED (except for in the DDR's last ever election which was also the first where people could actually vote for more than one party), which somehow always totally dominated the parliament, and the other parties representatives also always voted the SED line, but it was of course all "voluntary".

Setting up the electoral system so that real opposition is near impossible is a gentler approach than actually outlawing opposition. Or make actual opposition start from an extreme financial handicap.

Mao, which we'll get back to, also provides plenty of demonstrations of how to do this without making it explicitly illegal: A central element of the Cultural Revolution was to build up a "social movement" that would fight supposed capitalists and counter-revolutionaries, but implicitly also anyone opposing Mao, and let a bunch of misled youth do the dirty work (not unlike Hitlerjugend). A lot of their work then later led to trumped up charges or various people recanting or "voluntarily" relinquishing their power.

If you want to make it look like you have popular support, it's much better to let "social movements" harass the opposition than to do it yourself, but not any less authoritarian.

> When there is any political ideology it is illegal to espouse that does not involve directly inciting people to commit crimes?

Most Soviet-era dictatorships would argue that they did just fine on this. You could espouse anything that wouldn't incite people to commit crime, they'd say. Of course espousing capitalism or actual democratic rights would be interpreted as inciting people to commit crimes.

> When it becomes illegal to stage mass protests about anything?

Even most Western democracies require permits for mass protests, and this is easy to exploit. A typical authoritarian government response to this is to make it legal, but only give permission when the protests are not seen as a threat, or to copy approaches also used by democratic states: Kettling, "Free speech zones", or simply refusing permits on security groups, or approving it for a time/date that kills its impact.

But a smart authoritarian government will welcome demonstrations that are not seen as a threat, or that are aligned with their interests. Mao's Cultural Revolution is a good example of mass demonstrations being used in support of an authoritarian government.

> When the media is directly owned by the state, as it is in many places?

What about when the media are owned by companies that know full well they exist only at the grace of government and "behave" and/or are owned by people beholden to the government? The effect is entirely the same.

> When journalists and activists are jailed, as they are in many places?

Inventing other crimes is easy. So is intimidating them instead of jailing them. Jailing them is the unsophisticated approach.

> When the media feels in any way uncomfortable roundly criticizing the government?

There's a sliding scale here that is incredibly hard to judge, because a lot of the time the media is "uncomfortable" criticising the government because they care about access, or because they don't think their audience or their advertisers will want to read/hear/watch it. Arguably the US is already in a situation where it takes extreme situations before the major media outlets wants to rock the boat.

> When the media feels too uncomfortable to openly publish government secrets which were previously leaked?

I'll grant you this is probably a good indicator - I can't think of any examples of obviously authoritarian governments that'd tolerate this other than for documents obviously "leaked" with permission.

> When most people think the government is authoritarian and needs to be reined in?
> When enough people think the government is authoritarian that, under a democratic system, they would be a powerful voting bloc?

This doesn't make sense to me as it's incredibly hard to judge, and a government can be authoritarian but still be roughly aligned with the interests of a majority in a way that makes it seem relatively open on the surface. By the time a government is authoritarian, you won't be able to get good data on this.

> When at least enough people think the government is authoritarian for the idea to be given serious consideration in mainstream debates? (Debate about specific programs that need to be curtailed, without a general sense that the government is comparable to a police state, do not count.)

> When we don't see things happening like
> a rightwing antigovernment political movement becoming very popular and taking over a significant portion of the legislature;

You mean like the NSDAP? (Yes, I know what you're actually referring to, and no, I'm not trying to compare them to the NSDAP other than the fact the NSDAP also campaigned massively on how bad the establishment were doing, and got substantial public support, as have many other movements that have had both good and bad intentions).

This is making assumptions about the power structure of an authoritarian government that are too simple. There's been plenty of authoritarian government where "mass movements" were built promising massive change and an opposition to current government practices, but where they were used simply for internal power struggles and getting a "clean slate".

Again, Mao is a good example - the Cultural Revolution was used as a means to imprison or disgrace a long list of high powered opponents of Mao, some, like Deng Xiaoping, who later eventually managed to run China despite never taking the posts that would have given him official leadership (making him another good example of how looking at formalities of who are officially in charge doesn't work very well).

> a leftwing anticapitalist political movement staging provocative long-term demonstrations around the country with, at the end of the day, mostly pretty reasonable interactions with various municipal police departments, and managing at least to significantly influence the debate;

Occupy was never a threat to anyone - it was horribly disorganised, had no understanding of actual left wing politics or the history of these kind of struggles in the US to the point where they were largely a joke. If anything "occupy" was a useful outlet to let people take out their frustrations without achieving much. A smart authoritarian government should "encourage" demonstrations like that - if nothing else they'd be greatly useful in charting "persons of interest".

Mao is again a perfect example of why "influencing the debate" in itself is meaningless: His "Hundred flowers campaign" is a textbook example of how to encourage debate, give the debaters room to get their frustrations out, and then shut the door (option extra for advanced authoritarians: carefully observe the debates and take note of who might be a continued threat, and find ways of making sure they aren't - up to and including arrest, or simply ensure they are ridiculed).

> a judge placing harsh limits on a practice by a city's police department that was found to be unconstitutional?

What about high level officials being arrested for corruption and abuse of powers? http://www.bbc.co.uk/news/world-asia-china-23776348
China prosecutes or persecutes even high level party officials on a semi-regular basis, and has since Mao's time (e.g. again Deng Xiaoping is a good example) - it's a great way of getting rid of people that have lost internal power struggles while giving an aura of accountability. It's also just good practice to apply harsh limits on parts of governments that does not impact your ability to rule - the more people are led to believe that the government does actually abide by the rules the less impetus there is to rebellion even if everyone realises that they live in an authoritarian state.