Of the nearly 4,000 letters mailed this month by Secretary of State Scott Gessler to suspected noncitizens — asking that they prove they are eligible to vote or remove themselves from the voter rolls — 12.45 percent went to Republicans, prompting critics to again question whether the effort is politically motivated.

Gessler, a Republican, has strongly denied the allegation that his effort to block noncitizens from voting is intended to keep left-leaning voters from going to the polls in November.

Of the 3,903 letters mailed, the largest number — 1,794 — was sent to unaffiliated voters, while 1,566 went to Democrats and 486 to Republicans. The other 57 went to other parties.

As of Aug. 1, Colorado’s registered voters were 35 percent unaffiliated, 33 percent Republicans and 32 percent Democrats.

“It makes me suspect, and it should make the people of the state suspect, what his true motivations are,” state Rep. Crisanta Duran, a Denver Democrat, said, referring to Gessler.

The numbers were first reported Monday by The Associated Press.

Richard Coolidge, communications director for Gessler, said the office did not look at voter affiliation before compiling the list or mailing the letters and that the information was compiled only after the Associated Press requested it.

He declined to respond to allegations of partisanship by the secretary of state, calling it “political noise.”

The letters were mailed to registered voters who at some point applied for a driver’s license using noncitizen identification, such as a green card. Gessler’s office has acknowledged that some of those people could have been accidentally registered when they applied for their driver’s license or that they may have become citizens since they used the noncitizen ID.

The letters ask recipients to either provide proof of citizenship or remove themselves from the voter rolls.

Hearings will be held on any voter who was mailed a letter but does not respond.

Gessler has said identifying whether there are noncitizens on the rolls will help ensure the integrity of Colorado elections.

But Colorado Democratic Party chairman Rick Palacio said Monday he worries there may be unintended consequences.

“Regardless of their party affiliation, many of the people receiving these letters are being caught up in a rushed process that may fail to follow the law,” Palacio said. “Even more troubling than the political affiliation of these people is the possibility that American citizens who are eligible to vote are being denied their right to do so.”

Gessler’s office has denied a Colorado Open Records Act request from The Denver Post for information on who was mailed letters, saying it is “part of an ongoing administrative investigation.”

Sara Burnett: 303-954-1661, sburnett@denverpost.com or twitter.com/sara_burnett