(Promoted by Colorado Pols)
POLS UPDATE #4: The Denver Post’s John Frank:
The signature of one voter, Pam Niemczyk of Littleton, raised particular questions because it appeared on two petitions in different handwriting.
Niemczyk said she remembers signing a petition for Graham outside a local grocery store but not Keyser.
“I have seen my signature for Jack Graham and I have seen my signature for Jon Keyser and I can definitely say the one for Jon Keyser is not my signature,” she said in an interview. “It’s forged.” [Pols emphasis]
POLS UPDATE #3: Coincidentally, a former candidate for Denver city council was just sentenced today by the Denver District Attorney’s office for falsifying signatures on a petition for ballot access.
POLS UPDATE #2: Marshall Zelinger at 7NEWS reports, bad news for Jon Keyser:
Pamela Niemczyk of Littleton told Denver7’s Marshall Zelinger on Tuesday that she had signed a petition for Jack Graham, another Republican U.S. Senate candidate. She said the signature on the Keyser petition was not hers, calling it a “fraud.” [Pols emphasis]
…The Keyser campaign issued a statement blasting U.S. Sen. Michael Bennet, the Democratic incumbent whom he and other Republican candidates are vying to challenge in the November general election.
“Senator Michael Bennet’s liberal friends, ProgressNow Colorado, embarrassed his campaign yet again today with a flailing stunt that clearly telegraphs to the entire political world how scared Michael Bennet is to face Jon Keyser in November,” Keyser spokesman Matt Connelly said in the statement. “…The entire political world knows Jon Keyser will be on the ballot and we appreciate Progress Now’s invitation to highlight for conservatives across the country that Jon Keyser is Senator Bennet’s worst nightmare.”
Whether or not it was political stunt, Denver7 confirmed that the Littleton voter said someone forged her signature on the Keyser petition.
POLS UPDATE: This could be about to get very serious for Jon Keyser, as 7NEWS’ Marshall Zelinger confirms apparent fraud in Keyser’s submitted petitions:
Watch this space for updates, uh-oh…
With time running out on a temporary injunction against the finalization of the 2016 Republican U.S. Senate primary ballot, ProgressNow Colorado, the state’s largest online progressive advocacy organization, called on the Colorado Secretary of State’s office to re-examine petition signatures submitted in the U.S. Senate race. This request comes after a cursory investigation of the Secretary of State’s own data revealed several invalid petition signatures that evidently slipped through the cracks, and at least one wrongly accepted duplicate signature that appears to be fraudulent.
“Our review of just a sample of Jon Keyser’s petitions in one congressional district has found enough uncaught invalid signatures to raise serious questions about whether Jon Keyser has in fact qualified for the Republican primary ballot,” said ProgressNow Colorado political director Alan Franklin. “The Secretary of State must immediately rescind their statement of sufficiency for Jon Keyser, and request an extension of the temporary injunction now in place to revisit errors and potential fraud in the signature validation process. ‘Close enough’ isn’t good enough for Colorado voters.”
After petition documents were made available for inspection by the Colorado Secretary of State’s office, a cursory review of Jon Keyser’s signatures in one congressional district found at least six invalid duplicate signatures that were not discarded in the Secretary of State’s signature validation process. The signatories appear in the accepted signature reports for both U.S. Senate candidates Jack Graham and Jon Keyser. Based on Keyser’s total validated petition signatures in one congressional district (CD-1), fourteen additional invalid signatures would put Keyser below the minimum number required to appear on the 2016 ballot.
At least one duplicate signature accepted for Keyser, a voter whose signature was also accepted for Jack Graham, appears to be fraudulent. A visual inspection of the signatures plainly shows the same name filled out in different handwriting. 
“Our brief look at the petitions for Jon Keyser has raised serious questions, and after he barely qualified for the ballot, every single signature matters,” said Franklin. “Our sample of petition signatures has revealed previously uncaught errors, as well as a potential for outright fraud, that could change everything in this race. Unless the Secretary of State takes the time to re-verify every petition signature, no one can have confidence in the Republican U.S. Senate primary ballot.”