2016 US presidential elections: Iowa casts first votes

Donald Trump and Hillary Clinton are hoping to win the opening test in Iowa

The battle to elect the next president of the United States got underway, with frontrunners Donald Trump and Hillary Clinton hoping to win the opening test in Iowa, the first state to cast votes.

After months of campaigning during which Trump and other political outsiders have ripped up the script, voters in this midwestern state filed into church basements, school gymnasiums and libraries to have their say in the caucuses.

The contests in both parties are tight.

Trump has led the Republican polls for months, savaging early favorite Jeb Bush, and putting the rest of the large field -- 12 in all -- on the back foot.

But the controversial billionaire now faces a stiff test from ultra-conservative Senator Ted Cruz, who has invested heavily on the ground, hoping to get an early lead in the months-long race for the party's nomination.

"What a bit of history we are seeing," Cruz told fired up supporters yesterday.

However, political upsets are commonplace in Iowa: Will an establishment Republican -- Senator Marco Rubio, perhaps -- confound the polls and make it a three-way race?

For the Democrats, Clinton is looking to lay to rest the demons of 2008, when she lost in Iowa to now-President Barack Obama, and pursue her quest for history by dealing a solid blow to her upstart challenger Bernie Sanders.

"I know how to do this and I'm ready," a confident Clinton, vying to be America's first female president, told CNN hours before voting.

"There is just a lot of excitement and energy. I'm urging everybody to come out and caucus tonight to be part of this unique American process."

At most, a few hundred thousand people are expected to attend, highlighting the importance of voter turnout in an Iowa race where success can be the bedrock to a candidate's long-term success.

For both parties, most caucus meetings began at 7:00 p.m (local time), and results are expected within hours. Such meetings to select candidates for each party take the place of primaries.

But it is not just Iowa that is up for grabs -- so too is the early momentum candidates are craving in the presidential race ahead of next week's primary in New Hampshire.

Clinton is under intense pressure to win here before going back to New Hampshire where Sanders, who is from neighboring Vermont, holds a strong lead.

Sanders, who describes himself as a democratic socialist, declared his race with Clinton a "toss-up."

A Quinnipiac University poll of likely Iowa voters released yesterday agrees, showing Sanders even edging in front of Clinton, 46 to 43% -- within the margin of error of 3.2% points.

Pollsters said Sanders' success would depend on turnout among first-time caucus participants. Sanders has energized young Democrats with his denunciations of the "billionaire class" and his calls for a political revolution.

"If the turnout is high, I think we've got a real shot to win this," Sanders told CNN's "State of the Union" program.