Republican presidential candidate Donald Trump is telling his supporters he believes this 2016 election is stacked against him.

Bexar County Republican Chairman Robert Stovall said he is concerned about the same thing.

"We've been hollering about this for several election cycles," Stovall said. "We know that fraud has taken place but it's hard to complain about it after it over."

He said this is what caused twice as many people to volunteer to work polls.

Poll watchers have been trained to go to the polling locations and be ready for any situation that may look suspicious.

"It’s a serious thing if somebody gets a utility bill or a phone bill or something like that and says that they're you," Stovall said. "All that they need to do is walk into the polling location prior to you voting and they vote for you and if you go in after that and claim that that wasn't you then your ballot becomes an alternate ballot and probably will not be counted."

However, Bexar County Election Commissioner Jacque Callanen said there is a system of checks and balances that makes voter fraud almost impossible.

"We know exactly where every [voting] unit is, who's touched it," Callanen said. "We have background checks on the people who program, all our staff members, the transportation company that delivers them."

During the weeks leading up to the elections, Callanen and elections department workers are going through dry runs with the polling units.

The team is making sure that the number of votes going in are the same as the results coming out.

"It's completely independent," Callanen said. "You can just have one unit standing there, you can vote on it, it's not tied to anything else."

She said that the 254 Texas counties act as separate independent agencies, working for the voters and people in their county.

"Our numbers are going up and we take care of Bexar County voters," Callanen said. "I have full confidence in the integrity of the election in Bexar County."