BOISE - As Democrats throughout Idaho make their choice for president Tuesday night, Ada County is seeing a huge turnout for its caucus.

Organizers tell KTVB that they will start late due to thousands of people still waiting to get into the Boise Centre. A long line formed early and stretched around the block and down the street.

MORE: Guide to Idaho's Democratic caucuses

The doors were set to close at 7 p.m., but that was extended to allow more time to get people processed and inside. Organizers planned to cap the line at 7 p.m., but wanted to make sure those who have been waiting for hours were able to get in.

Just before 8 p.m., organizers began handing out caucus ballots to people waiting in line. One worker said, "You are participating in the largest caucus in the history of the United States."

An overflow area was opened at CenturyLink Arena next door.

Canyon County's caucus at Sage Valley Middle School also got a late start Tuesday night. Caucusing began about an hour late, organizers said, after a larger than expected crowd showed up.

Nearly 1,800 people attended the caucus.

"We had a lot more people than we were equipped to handle," said Bob Solomon, chair of the Canyon County Democrats. "We did the best we could. People were patient and of good cheer."

Elsewhere in Idaho, Bannock and Kootenai counties also had to make last-minute changes to accommodate the large crowds. In Blaine County, nearly 900 people turned up at Hailey's Wood River High School, doubling the numbers from 2008.

With more than 21,000 voters expected to caucus statewide, party leaders were hoping for a repeat of 2008, when a record number of people participated in the state's caucuses.