With Massachusetts Sen. John Kerry emerging as the likely next secretary of state, speculation is rising on whether state Democrats can hold onto his Senate seat.

As chairman of the Senate Foreign Relations Committee, Kerry has been a top contender for the spot since Secretary of State Hillary Clinton announced she will not stay during President Obama's second term.

Kerry emerged as the leading candidate after embattled U.S. Ambassador to the United Nations Susan Rice withdrew Thursday from the running.

The speculation about Kerry and the Massachusetts senate sweepstakes intensified Saturday after a source told Fox News that Obama has picked Kerry -- opening the door for a special state election and a potential candidacy for Republican Sen. Scott Brown who lost his reelection bid last month.

It's now basically a done deal," said the source. 

Brown would again face a tough challenge, considering Massachusetts is a heavily Democratic state. However, state law calls for a special election, not a gubernatorial appointment, and Brown has pulled off an upset before.

Massachusetts created a law in 2004 that calls for a special election to fill a U.S. Senate seat.

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