Mr da Silva has invited their small, soft-left parties to join him in government.
And just like Mr da Costa, he seems to lack his running mate's trust.
ECONOMIST: The stakes are high for the hapless running-mates
Mr da Silva needs to persuade investors that he is not abandoning economic reforms.
Despite his comfortable lead at present, Mr da Silva's victory is by no means assured.
But Mr da Silva is distrusted by many voters, and is unlikely to win.
But the president seems reluctant to sour his relations with Mr da Silva, his more probable successor.
Mr da Silva has dismayed markets by saying that Arminio Fraga, Brazil's trusted central-bank chief, must go.
As Mr Cardoso's propagandists are busy reminding them, in 1994 Mr da Silva opposed the real plan.
In any case, despite his comfortable lead at present, Mr da Silva's victory is far from assured.
But if not, and if Mr Gomes goes through to the run-offs against Mr da Silva, what then?
To help Mr da Silva win last year's election, it ordered a moratorium on land invasions during the campaign.
Mr da Silva is well aware that it was the prospect of his victory which initially unnerved the markets.
For either Mr da Silva or Mr Serra, that would be a calamitous start to their term of office.
PT's municipal boost, Mr da Silva is unlikely to be Brazil's next president.
Mr da Silva, who stood for the presidency in 1989 and 1994, has built up a strong personal following.
Mr da Silva has now tried and failed three times for the presidency.
So Mr da Silva is going to have to work quickly and effectively.
But there are few areas where Mr da Silva has been so specific.
In fact, a victorious Mr da Silva would face some difficult political choices.
Once in office, Mr da Silva would not want to disappoint his supporters.
It is plagued by rumours that Mr da Silva will sack hardline directors.
Using such televised debates to expose Mr da Silva's weak grasp of policy details is probably Mr Serra's best hope.
With two weeks to go, Mr da Silva's slim hopes rest on picking up enough votes to enforce a run-off.
And over twice as many, polls say, trust him to steer Brazil through the turmoil as trust Mr da Silva.
Mr da Silva, likewise, could keep reiterating a recent pledge to maintain a sufficient primary surplus to stabilise the government-debt ratio.
So Mr da Silva would be stuck in the dilemma common to many left-wing governments taking office for the first time.
Jittery Brazilians did not like opinion polls showing Mr da Silva with a big lead over Jose Serra, the markets' preferred candidate.
Though Mr da Silva won almost exactly twice as many votes as Mr Serra, the run-off is not quite a foregone conclusion.
If Mr da Silva wants to be sure of avoiding such a fate, he must act fast and he must act convincingly.
This is Mr da Silva's fourth election campaign, and he has been ahead in the polls at this stage in the past.
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