Occasional press speculation about U.S. Sen. Amy Klobuchar's prospects as a 2016 presidential contender has taken a new twist in light of recent reports that she signed on to a "private" letter with 15 other women in the Senate urging Hillary Rodham Clinton to run.

The letter, first reported by ABC News, also includes the signatures of potential Democratic rivals Sen. Elizabeth Warren of Massachusetts and Kirsten Gillibrand of New York.

Reportedly organized by Sen. Barbara Boxer of California, the letter has the signatures of all the female Democrats in the Senate.

Although Klobuchar not infrequently makes it onto speculative media lists as a third-tier presidential contender, aides say she has publicly urged Clinton to run before.