Hillary Rodham Clinton is expected to announce her 2016 campaign for president as early as this weekend, according to several published reports.

The former secretary of state and U.S. senator from New York, considered an early favorite to win the Democratic nomination, will likely make the announcement that she is running via social media, according to reports in The Wall Street Journal and Reuters.

Clinton sources who spoke to the Journal, however, declined to confirm a report in the New York Daily News that the official declaration would happen Sunday.

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News broke last week that Clinton, 67, who lives in Chappaqua, chose a Brooklyn Heights building as her all-but-declared campaign headquarters. That move started the clock ticking on the announcement of her presidential intentions because federal election rules dictate a formal candidacy declaration or formation of an exploratory committee within 15 days of such campaign activity.

Clinton, who ran for president unsuccessfully against President Barack Obama in 2008, may have primary competition. No other Democrat has entered the 2016 race, though former Maryland Gov. Martin O'Malley has signaled he may run, and Vice President Joe Biden is said to be exploring a possible run.

Lincoln Chafee, a former Republican senator from Rhode Island who left the party in 2007 to become an independent before serving as the state's governor and who is now a Democrat, and former Sen. Jim Webb of Virginia, have both formed exploratory committees. Sen. Bernie Sanders (I-Vermont) has said he is considering entering the Democratic contest.

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Clinton's initial campaign events are expected to be held in Iowa and New Hampshire, the first states to vote in the presidential primary contest, according to The Associated Press.

On the GOP side, Sen. Rand Paul of Kentucky and Sen. Ted Cruz of Texas have declared their candidacies for president.

Former Florida Gov. Jeb Bush has formed an exploratory committee. Sen Marco Rubio of Florida reportedly will announce his candidacy next week.