Sources: Kaine, Vilsack top Clinton's running mate list

Virginia Sen. Tim Kaine and Agriculture Secretary Tom Vilsack have emerged as the top two choices to be Hillary Clinton's running mate, campaign sources told Fox News.

Kaine, the former governor of the battleground state, is said to be the leading contender.

However, Vilsack is a longtime friend of the Clintons and was described as a "strong" second choice.

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