The Colorado Secretary of State's office says investigators are ready to respond if any voting irregularities are reported.
There have already been at least two reports of voting machine malfunctions.
In Adams County and Pueblo, people said machines were switching their votes. Investigators from both parties checked out the machines and could not duplicate the issues.
On the eve of Election Day, a team of state investigators traveled from Denver to Pueblo.
Colorado Secretary of State Scott Gessler says his team tried to reproduce the problem, under the close supervision of Democrats and Republicans.
"Our office is always vigilant. We had some complaints and concerns that the touch screen machines were taking a Romney vote and registering it as an Obama vote. At this point, we're saying that we can't identify a problem with the equipment itself and we've exhausted pretty much every avenue that we can in our investigation," Gessler said.
Pueblo County Clerk and Recorder Gilbert Ortiz believes human error caused the problems.
"How many more times has this occurred? None of us know. And this could have a significant effect on the election in this county," Pueblo voter Chuck Schneider told KRDO-TV.
Gessler says the machines in question won't be used on Election Day.
The Colorado Secretary of State's office got reports of a similar issue in Adams County last week.
"The two [Adams County] machines were pulled offline. We didn't find problems there," Gessler said.
In a battleground state like Colorado, every vote counts. Counting those votes fairly is the mission of a bipartisan team, working out of what's called the "war room."
"Hopefully we can resolve problems here in the office right away before they escalate and fix them," Gessler said.
Thousands of volunteers will be manning the polls statewide. There are 400,000 more registered voters today than there were four years ago, a 13-percent jump.
Colorado will be under scrutiny, as the results here could shape the outcome of a close presidential race.
"Lots of preparedness. Lots of hard work. We're used to this attention and this focus," Gessler said.
If you have a mail-in ballot in your hand, don't put it in the mail. Make sure you turn-in your ballot, in-person, to a polling place or your county elections office.
The County Clerk and Recorder has to receive the ballot by 7 p.m. on Election Day for it to be counted.
To check the status of your mail-in ballot or learn where your polling place is on Election Day, go to: www.GoVoteColorado.com.
(KUSA-TV © 2012 Multimedia Holdings Corporation)