Colorado Democrats piled on Republican U.S. Senate candidate Jon Keyser Friday after the prominent fact-checking organization PolitiFact awarded its strongest “Pants on Fire!” designation to a claim the former state lawmaker made in a TV ad his campaign began airing this week, but the Keyser campaign disputed the ruling and stuck to its guns.

Listing a number of recent controversies that have bedeviled the Keyser campaign – including allegations that fraudulent petition signatures helped him qualify for the June primary ballot and that his claim he’s been a “lifelong Republican” is contradicted by two years he switched to unaffiliated status – a spokesman for the Colorado Democratic Party laid into the candidate.

“Jon Keyser is now developing a reputation amongst Coloradans that he can’t be trusted about his own record – or anyone else’s,” said Chris Meagher in a statement. “From submitting forged signatures to producing ads filled with ‘ridiculous’ and ‘false’ statements to misleading Colorado voters about his voter registration history, it’s truly been a banner week for Keyser.”

Keyser is one of five GOP candidates vying in a June primary for the chance to take on U.S. Sen. Michael Bennet, the Democratic incumbent. The other Republicans in the running are El Paso County Commissioner Darryl Glenn, Colorado Springs businessman Robert Blaha, Fort Collins businessman Jack Graham and former Aurora City Councilman Ryan Frazier.

On Thursday, PolitiFact Colorado, in partnership with the Denver7 news crew, examined Keyser’s characterization of the nuclear deal with Iran in a 30-second ad that began airing on the Fox News Channel the same day. “Obama wants to give [Iran] nuclear weapons, and Michael Bennet, he was all for it,” says Keyser, a major in the Air Force Reserve and a combat veteran in Iraq and Afghanistan.

“Keyser portrays the agreement as a plot to arm Iran with nukes when it’s designed to do exactly the opposite,” PolitiFact writes after a lengthy examination of the deal and Bennet’s positions and proposals surrounding it, and then concludes: “It’s ridiculous to say Obama and Bennet wanted this deal because they want to give Iran a nuclear weapon. We rate the statement Pants on Fire!”

But a Keyser campaign spokesman swung back, charging that Bennet’s support for the nuclear deal with the “world’s largest state sponsor of terrorism” – as Keyser referred to Iran in a tweet on Thursday – means exactly what the Republican candidate says it does.

“Since Michael Bennet voted to give Iran an extra $150 billion to fund their terrorist activities, Iran has flouted the international community by testing ballistic missiles, captured American sailors, and wrote ‘Israel Must Be Wiped Out’ on their missiles,” said Matt Connelly, Keyser’s communications director, in a statement. “Sen. Bennet may live in a dream world where the Iranian regime will magically abide by the rules and give up their destructive behavior, but the reality of the situation is that his vote for the Iran deal was clearly a vote to give them nuclear weapons.”

It’s only the third time this cycle PolitiFact Colorado has weighed in on statements made by U.S. Senate candidates in Colorado. In early March, the organization labeled as “False” another Keyser claim, that Bennet wanted to close the Guantanamo Bay prison and bring terrorists “right here to Colorado.” A month later, PolitiFact Colorado labeled as “False” a statement by Graham, that “it’s clear” Democratic presidential candidate Hillary Clinton “violated national security laws.”

Six years ago, when Bennet was running for his first full term in the Senate, PolitiFact rated as “Mostly False” the National Republican Senatorial Committee’s charge that the Democrat “cast the deciding vote” for the massive stimulus plan and the equally massive health care reform package that came to be known as Obamacare, even though Bennet voted for both. The organization ruled, however, that President Obama’s pledge “If you like your health care plan, you can keep it” was the “Lie of the Year” in 2013.

– ernest@coloradostatesman.com