By ABC's Barrie Cassidy

Photo: What changed that made Arthur Sinodinos have to stand aside? (AAP: Alan Porritt)

Clive Palmer's new demands over the mining tax repeal come at an already difficult time for Tony Abbott, who has questions to answer over his embattled Assistant Treasurer, Arthur Sinodinos, stepping down, writes Barrie Cassidy.

Clive Palmer has now put a price on his support for the repeal of the mining tax; a very small price in monetary terms, but one that will annoy and embarrass the Prime Minister just the same.

It had always been assumed that Palmer's bloc of three votes in the Senate would negate the combined Labor and Greens vote and allow the repeal of both the carbon and mining taxes with no strings attached.

But now Palmer in an interview with Fran Kelly on Radio National has put an awkward proposition to the Government.

He insists it has to backdown on the decision to end the bonus welfare payments to the children of war veterans injured or killed overseas. The payments go to 1240 recipients and cost in total just $260,000 a year. They are essentially education allowances to cover unforseen expenses.

But Tony Abbott has insisted that because the payments were to be paid for by the mining tax, and the mining tax didn't raise any revenue, then they have to go. It's the principle.

Now if the Government wants to achieve one of its major reforms, it will have to swallow its pride and give in.

Palmer told the ABC: "We think that if a person's given their life for Australia, they should be assured the government's not going to attack the children after they're gone."

The government, he said, should not "persecute" children.

Though the demand is small, it says much about Palmer. Nothing can be taken for granted, no matter what the issue. And he's going to have his own pet issues along the way.

It was a big call for him given that his support for the repeal of the mining tax would doubtless help his chances in the West Australian Senate election. But he is assuming that money for the "orphans", as some emotively describe it, will be the bigger issue in the mind of the electorate.

It was for the Government another headache it didn't need on top of the decision by the Assistant Treasurer, Senator Arthur Sinodinos, to step aside while a corruption inquiry investigates his business dealings.

Sinodinos has taken one for the team, lowering the temperature on the issue in the run-up to one of the most important budgets any government has delivered in a long time.

However, his gesture drew attention to the Prime Minister's handling of the matter. Why was it OK for Sinodinos to stay in his job on Tuesday and yet by Wednesday it was "in the best and most honourable Westminster tradition" that he stand aside? What changed?

And going back even further, why was Sinodinos made Assistant Treasurer in the first place when details of the emerging scandal were known to everybody?

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And then of course there were the routine questions to deal with as well. What did the Prime Minister know and when did he know it? What conversations were held between the two, and whose decision was it that he should walk?

For Sinodinos to resume his ministerial career, he will need to be exonerated by the inquiry. There cannot be any ambiguity or lasting suspicion.

Counsel assisting the inquiry, Geoffrey Watson SC, made no direct allegation against the Senator. Neither has anybody else.

However, the counsel did insist Sinodinos was hired on excessive remuneration by Australian Water Holdings to open up lines of communication with the Liberal Party, and that he stood to gain many millions if the company gained a contract with Sydney Water.

Ominously, Watson added: "He has other involvements that will come under scrutiny," an apparent reference to donations made to the Liberal Party.

Not only does Sinodinos insist he knew nothing of the Obeid connection with the company, he also denies any knowledge of the donations. At one stage, Sinodinos was chairman of the company making the donations and treasurer of the party receiving them.

The Obeid name has now taken on the poisonous connotation of the disgraced former West Australian premier Brian Burke's name back in 2007.

Then, John Howard made much of Kevin Rudd's meetings with Burke, only to find one of his own ministers, Ian Campbell, had met with Burke.

Campbell resigned.

With both Obeid and Burke, attempts by the Coalition to condemn Labor figures as guilty by association badly backfired.

Barrie Cassidy is the presenter of the ABC program Insiders. View his full profile here.

What changed? Questions for Abbott about Sinodinos - The Drum (Australian Broadcasting Corporation)