DES MOINES, United States, Feb. 1 (Xinhua) — The 2016 U.S. presidential race formally began Monday in the mid-western state of Iowa, as Iowans were gathering in some 1,681 precincts to make their choices among the candidates in the state's caucuses.

Three candidates, including former Secretary of State Hillary Clinton, are competing to be the standard-bearer of the Democratic Party, while the Republican field includes New York billionaire developer Donald Trump, former Florida Governor Jeb Bush, and nine other candidates.

The caucuses began at 7 p.m. local time and they go until they are finished. Unlike primaries, where statewide secret ballots are held, caucuses are local gatherings of party members who openly show support for candidates.

For decades, the Iowa caucuses have been running ahead of primary elections in other states, and the results of the first formal contest for the presidential race have long been widely regarded as early indications of which candidates might win the final nomination.

"We're a small state, but we're the first to have a real vote for the Iowa caucuses," said Iowa Governor Terry Branstad. "If you want to run for the president, you would like to win the first contest."

According to the final poll before Iowa caucuses, released on Saturday by the Des Moines Register/Bloomberg Politics, Clinton led Senator Bernie Sanders by a mere 3 percentage points among likely Democratic caucusgoers, while Trump leads his major Republican rival and Texas Senator Ted Cruz by 28 percent to 23 percent in Iowa. Enditem