Hong Kong (CNN) Thousands are marching through the streets of Hong Kong for the annual July 1 protest to call for democracy in the Chinese-administered territory.

This year's march was going to be led by bookseller Lam Wing-kee, who says that he, along with four colleagues, was kidnapped by Chinese agents for publishing books critical of President Xi Jinping and other top officials. However, citing safety concerns, Lam decided not to attend the rally, the march's organizers announced Friday.

Lam's revelations sparked outrage in the city and have further strained relations with China. Marchers called for the resignation of Hong Kong's top official, chief executive Leung Chun-ying. In China, video of the protest on CNN was blacked out.

Earlier, the government marked the 19th anniversary of the handover of Hong Kong from British to Chinese rule with a flag-raising ceremony at Golden Bauhinia Square near the city's business district.

Thousands have marched through the streets on July 1 since 2003, when numbers peaked at more than 400,000. Far fewer were expected this year, after last year's low turnout following the 2014 mass Occupy protest.

CNN spoke to long-term lawmakers and some of the young guns seeking to replace them. Interviews have been condensed and edited for clarity.

Hong Kong's relationship with China

Alan Leong, lawmaker, Civic Party: I've seen Hong Kong going down the mainlandization route at a pace much faster than we can swallow.

Hong Kongers, particularly the youth, feel a sense of hopelessness and they want to take things into their own hands instead of trusting the institutions and the political parties who according to them have failed to deliver change in the past three decades.

Holden Chow, vice-chairman, DAB: I strongly believe that "One Country, Two Systems" generally works well. Because first of all, we have our rule of law here, and the Basic Law (Hong Kong's mini-constitution) guarantees the rights and freedoms we enjoy.

Regina Ip, lawmaker, New People's Party: We need to hold up the authority of the Central Government, but also want to maintain Hong Kong's high level of autonomy.

You are bound to have underlying tensions when you have two radically different systems under one roof.

Edward Leung, spokesperson, HK Indigenous: I don't think Hong Kong should change only when China changes. Our change shouldn't be defined by another change in another place.

Cyd Ho, lawmaker, Labour Party: We don't have true "One Country, Two Systems" now because of increasing interference by Beijing in Hong Kong. We need to fight for the "Two Systems" part.

Hong Kong people didn't have a say when China and the UK negotiated its future. Our democracy movement's biggest failure was not fighting harder for a democratic framework under British rule. It would have been easier then than now.

Calls for Hong Kong independence

Nathan Law, chairman, Demosisto: The conditions for independence, which we don't currently have, need to be based on practical situations. They include whether we can have a self-sufficient society, whether people have a shared vision for an independent Hong Kong and its future, and whether a large number of people could accept (the idea of) independence.

We hope to organize a civil referendum in the future to bolster the consensus in society that Hong Kongers should have the right to decide their own future.

Regina Ip, New People's Party: I think the great majority of Hong Kong people know that Hong Kong independence is neither legal, constitutional nor workable. It is simply not workable. What they're asking for is so-called "real self-determination" but in effect it amounts to secession (from China).

We're dependent on the mainland for our water, our power supply, our food. If we break away from mainland China, our economy would collapse.

Edward Leung, HK Indigenous: Independence is the only way to achieve real autonomy. After the Umbrella Movement failed, we learned it's very difficult to achieve true democracy and autonomy without breaking with the Chinese Communist Party, without truly decolonizing. Our system is flawed because although we have a rule of law, there's an authoritarian regime above it that could interpret and redefine our constitution.

Our Basic Law doesn't have any legitimacy and consent from the people. Trying to amend the constitution is to give our consent to this constitution once more. This will undermine the argument for independence.

Alan Leong, Civic Party: If things continue like they are and if a referendum is done after a decade with the option of independence, I really cannot rule out that we will end up like Brexit in the UK, that 52% will vote for independence.

But my hope is that we will never have to come to that. I hope that Beijing will come back to its senses.

Cyd Ho, Labour Party: Those who advocate for independence don't understand international relations. Even if independent, geographically our neighbors can affect us, just look at South and North Korea. It's naive to think that an independent Hong Kong would be fine without worrying about what goes on in China. What we need to do is strengthen our economy and various sectors, lessen our reliance on the mainland's market, and retain our ability to think critically.

Whether it's independence or self-determination, Hong Kong won't be able to achieve any of that if China doesn't become a civilized nation that respects human rights.

Split in Hong Kong politics

Alan Leong, Civic Party: The pan-democratic camp has been so divided particularly with the emergence of the youthful groups who have been flying the flag of the Umbrella Movement.

It's really a choice between a continued fight for democracy within institutions, or you support those who may not have a complete platform or agenda to offer as a protest vote.

Regina Ip, New People's Party: Polarization is inevitable. When you have a free society, and you have an open competition for popular support for different ideologies, you are bound to have a certain amount of polarization.

I believe that if we are able to progress further in our democratic development and if we have a popularly elected leader , who can act as a consensus politician, it would be easier to heal the polarization.

Holden Chow, DAB: As a politician here, I would like to restore the confidence of Hong Kong people in "One Country, Two Systems," which is a unique design that's never existed in any other jurisdictions.

Cyd Ho, Labour Party: Beijing has actually warmed up to the pan-democrats recently. Localists are their new enemy, they want to isolate this minority. We wouldn't join forces to isolate them as we have to defend freedom of speech even if we disagree with what is being said.

JUST WATCHED 'Ten Years' film predicts dark future for Hong Kong Replay More Videos ... MUST WATCH 'Ten Years' film predicts dark future for Hong Kong 03:03

Importance of July 1

Nathan Law, Demosisto: Leung Chun-ying's resignation should not be the focus of the march. What we need is a new political road map. If we follow the old one set by the pan-democrats, it's just going to be met with a series of disappointments. Whatever the fate of Hong Kong, gaining the right for self-determination and forming our own vision of Hong Kong's future is at the core of our work.

Alan Leong, Civic Party: I do not expect a large turnout (on July 1), but we should not underestimate the importance or significance of such marches.

So long as there is a not insubstantial amount of people coming out — just like the not insignificant number who joined the (June 4) vigil — I think the spirit will continue, the fight will go on.

Regina Ip, New People's Party: The Hong Kong Special Administrative Region is approaching its 20th anniversary. Many say we are reaching a critical period for "One Country, Two Systems."