US election 2016: Hillary Clinton's campaign for President sparks running mate buzz in US

Even before Hillary Clinton announced she was running for president this week, the buzz was all about her running mate should she become the Democratic Party nominee.

One of the most intriguing proposals is the current president, but other unusual ideas for her No. 2 include her husband — or a second female politician.

One of the challenges Clinton could face is that a 69-year-old white candidate won't inspire young voters and minorities — who played a key role in President Barack Obama's victories — to go to the polls. An obvious solution? Clinton could choose Obama to join her on the ticket, suggests the New Republic. It might be controversial but it's possible.

Under the American Constitution, Obama can't legally be elected for a third term, but that doesn't necessarily mean he couldn't step in for Clinton as president if she's incapacitated and serve a third term. But, on the downside, Obama could be a significant drag on Clinton's candidacy and fuel complaints that a Hillary Clinton administration would simply be a continuation of the current regime.

Another possible former president who could share her ticket would be husband Bill Clinton, who has some very obvious experience working at the White House. But he's a character who polarises opinion and would likely put a damper on Hillary's chances, claims the DemocratCafe.

Hillary would do better to rely on her husband - who might be termed the "First Laddie" if Hillary is elected - to be an effective campaigner for her, unlike last time around when the often overly-restricted Bill became cantankerous, notes Politico. This time Hillary is widely seen as more of her own woman so her campaign will be more likely to let Bill shine to his — and her — best advantage.

Other, far more likely running-mate possibilities include young, Hispanic and telegenic Housing and Urban Development Secretary Julian Castro, 39, a former mayor of San Antonio, Texas. Last summer Hillary and Bill Clinton invited Castro to their Washington home for dinner and a talk, sparking early speculation that he was already in the running for running mate, reported the Washington Post.

Castro's star can only be rising in a race for the Latino vote now that Florida Senator Marco Rubio has thrown his hat into the Republican ring. The Christian Science Monitor is already asking if a Clinton-Castro ticket is "inevitable," especially if it looks like Rubio is going to grab the GOP spot.

The New York Daily News thinks Castro has a strong shot at the spot, along with Massachusetts Gov. Deval Patrick — a charismatic African American interested in income inequality — Twitter star New Jersey Sen. Cory Booker, also African American, Agriculture Secretary Tom Vilsack, who's popular in swing-state Iowa where he served as governor, and Colorado Gov. John Hickenlooper.

Is Joe 'Biden' his time?

Vice President Joe Biden hasn't made a decision yet on whether to run for president, but either way, he's a possible Clinton running mate. Voters might be growing weary of him, but Bloomberg calls him an excellent candidate for another term as vice president, the office "he was born to fill." But Biden, 72, would be another older white candidate who wouldn't be the best choice to attract new and minority voters.

Could a double female ticket be a 2016 "dream team?" asks the Baltimore Sun. Progressive Massachusetts Sen. Elizabeth Warren, often talked of becoming a presidential candidate herself, could back up Clinton to sweep the female vote (though women don't necessarily vote for women).

The worst-case scenario? "Men will rise up in droves, horrified with the very idea of women running the country" and vote Republican, notes the tongue in cheek Sun.