It is the first electoral test for Conservative leader Mr Cameron since he became leader last December.

BBC: NEWS | UK | UK Politics | Tories are 'satisfied' with gains

His fixing skills found their greatest test when he served as Conservative chairman for two years up to the 1997 election.

BBC: Sir Brian Mawhinney

He said the company had sought to be conservative in its rollout by limiting the test to women with risk factors and recommending that it be administered in conjunction with genetic counseling.

WSJ: New Questions on Cutting-Edge Prenatal Tests

If the question becomes a test of whether he is a true conservative, many true conservatives will be confirmed in their suspicion that he is not.

ECONOMIST: Lexington

But that will test the promise of co-operation from his conservative adversaries in parliament.

ECONOMIST: Iran

That trick was successfully performed by Kenneth Baker, the Conservative Party chairman in 1990, when he manged to persuade the media that the real test of his party's popularity was what happened in the Tory showcase councils of Wandsworth and Westminster.

ECONOMIST: Local elections

The vote for town councillors in Spain's 8, 000 cities and villages, and for officials in 13 regional governments, is widely seen as the first test at the ballot box on whether Spaniards support or rebuke Aznar's conservative Popular Party for his support of the war.

CNN: Analysis: Spain seeks wider role

"His test is the way he handles the establishment, " says Aijaz Gillani, a conservative analyst.

CNN: CAN THIS MAN MEND PAKISTAN?

Now, this is perhaps the toughest test so far because there is one point separating Mr. Calderon, from the Conservative National Election Party, and Mr. Lopez Obrador, from the leftist Party of the Democratic Revolution.

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The real test of the leaders' power of persuasion will come with the one group they took for granted: conservative Republicans who question giving a single dollar to the United Nations.

CNN: Seeking Showdown With Clinton, Gingrich Gets One With GOP