Colorado Republican gubernatorial candidate Doug Robinson, a nephew of Mitt Romney, didn’t submit enough valid petition signatures to make the June primary ballot, the Colorado secretary of state’s office announced Friday, but the retired investment banker said he plans to appeal the decision.

Statewide candidates can qualify for the ballot through the caucus and assembly system or by turning in petitions with 1,500 signatures from registered voters in each of Colorado’s seven congressional districts, for a total of 10,500.

Election officials determined that 11,343 of the 17,391 signatures submitted by Robinson were valid, but he fell 22 signatures short in the 2nd Congressional District, which covers Boulder and Larimer counties and includes mountain counties along Interstate 70 to Vail.

But the Robinson campaign pushed back against that conclusion.

“We know we have the sufficient signatures, and we will be going to court,” Robinson campaign spokeswoman Brett Maney told Colorado Politics.

Meanwhile, Republican Victor Mitchell, a wealthy entrepreneur and former state lawmaker, qualified for the ballot with 14,515 valid signatures, the secretary of state’s office said.

He joins two candidates who made the primary at last weekend’s state GOP assembly – State Treasurer Walker Stapleton and former Parker Mayor Greg Lopez.

“I am so very gratified that so many Coloradans signed our petition,” Mitchell told Colorado Politics in a statement. “The petition campaign was done the right way, in accord with all the rules. It reflects the competent and ethical manner in which I will govern.”

Last week, Stapleton asked that his petitions – which had already been certified as sufficient – be withdrawn because some of the signatures might have been gathered by paid circulators who weren’t Colorado residents, as the law requires. Instead, Stapleton mounted a last-minute bid for delegate support. He wound up winning top-line on the ballot while at the same time keeping Attorney General Cynthia Coffman out of the gubernatorial primary.

Democratic Gov. John Hickenlooper is term-limited. Four Democrats have qualified for their party’s primary: former state Sen. Mike Johnston, former State Treasurer Cary Kennedy, U.S. Rep. Jared Polis and Lt. Gov. Donna Lynne, who learned Friday afternoon that she gathered more than enough signatures on her petitions.

The secretary of state has to certify the June 26 primary ballot by April 27.

This is a developing story and will be updated.