In this election campaign I have travelled to every province to make South Africans aware of the key choice in this election: between the ANC's closed, crony society for some and the DA's open, opportunity society for all.  This choice will mean the difference between success or failure for South Africa.  I have outlined our plans to create jobs, beat crime and alleviate poverty. I have demonstrated to people that life is better for everybody where the DA governs.

Now it is crunch time. The events of the past week have shown that Jacob Zuma is willing to use whatever means necessary to avoid his day in court and get a clear run to the presidency. Zuma now stands on the verge of winning a two-thirds majority to unilaterally change the Constitution to abuse power, advance his cronies, and protect them from being held accountable for corruption.

The DA will not stand back and let this happen. Yesterday, we launched our "STOP ZUMA" campaign to underscore the importance of preventing a Zuma two-thirds majority. Today, I will begin taking this message to South Africans all over the country - to places like Springbok, Polokwane and Butterworth.

This is why we have chartered this aeroplane. It will enable us to get to far-flung places that are difficult to travel to by road or on commercial airlines. We will be able to cover far more ground in one week than we usually do.

I will tell people the same thing wherever I go: Only the DA is big enough and strong enough to stop Zuma. Only the DA stands between Zuma and the failed state. If people do not unite behind the DA, Jacob Zuma may well secure the two-thirds majority he needs to unilaterally change the Constitution. The ANC already has plans to emasculate local governments led by the DA. And if the DA succeeds in its call for a judicial review of the NPA's decision to withdraw charges against Zuma on 783 counts of corruption, then it is entirely predictable that Zuma's ANC will change the Constitution to protect an incumbent President from facing corruption charges in court.  But this can happen only if the ANC gets the two-thirds electoral majority it needs to change the Constitution.

Zuma and his inner circle have already gone far in their determination to entrench their power, enrich themselves, and ensure they are immune from prosecution. So far, they have destroyed the Scorpions, they have pressurised the National Prosecuting Authority to drop Zuma's corruption charges and they have engineered the release of their crony, Schabir Shaik, from prison.

Next on their agenda is to remove every other obstacle to unfettered power. Press freedom, the independence of the judiciary and every section in the Constitution which limits the ruling party's power are under threat. When these institutions fail, the economy fails. When the economy fails, the poorest suffer. We only have to look north of our border to see how this downward spiral destroys the livelihoods of every person outside the small leadership clique of the ruling party.

The most important election in Zimbabwe was not last year when the MDC won more votes than Mugabe's Zanu-PF, despite the election being blatantly rigged. It was in 2000, when the MDC narrowly lost to Zanu-PF by 1% of the vote. If every MDC supporter had gone out to vote in that election, Zimbabwe's catastrophic slide may have been halted. Today Zimbabwe might have been the prosperous nation it once was, instead of the failed state it has become.

When we look back ten years from now, we must be able to say that we stopped ANC cronyism and corruption before it was too late. We must say that we stopped Zuma from getting the two-thirds majority he needed to change the Constitution.

This election can be a turning point in South Africa's history. If all our supporters come out to vote, we can stop a Zuma two-thirds majority and start the process of winning power from the ANC. This will start right here in the Western Cape where we have a very good chance of winning the province with an outright majority.

If we win the Western Cape, we will demonstrate - as we are in Cape Town - that life is better where the DA governs. We will show South Africa that there is an alternative to the closed, crony society. It is a society in which every South African - regardless of the colour of their skin or the circumstances of their birth - has the opportunity to make a success of their lives.

This is an extract of DA leader Helen Zille's speech to Democratic Alliance supporters as she departed for the first leg of her national plane tour this morning from Cape Town International Airport

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