Obama waits to announce his pick for No. 2

By John Whitesides, Political Correspondent

WASHINGTON (Reuters) - Democrat Barack Obama prolonged the suspense over his vice presidential pick on Friday, saying he had chosen an independent voice who could be an effective governing partner -- but not announcing the name.

Obama dragged out the unveiling of his No. 2 for maximum political impact, keeping pundits guessing and supporters waiting as he stayed out of public sight most of the day.

Obama, 47, a first-term Illinois senator, says he has decided on a running mate who will be prepared to step in as president, can help him govern and will be independent.

"I want somebody who is going to challenge my thinking and not simply be a yes person when it comes to policy-making," he said on CBS' "The Early Show."

The announcement could come at any time. Obama is expected to appear with his running mate on Saturday in his home state of Illinois as they launch their run to the Democratic convention in Denver.

The convention opens on Monday and the vice president will accept the nomination on Wednesday.

Obama will make the announcement of a vice president by text messages and e-mails to his list of more than 2 million supporters after stretching out the suspense about his choice for days.

"I'm pretty disciplined on this," Obama said on CBS.