Mitt Romney’s nephew Doug Robinson failed to make the ballot in Colorado’s governor’s race, a major shakeup in the Republican primary. The former investment banker did not submit enough valid voter signatures to qualify — falling 22 signatures short in one congressional district, the secretary of state’s office announced Friday. Robinson’s campaign said it would challenge the determination in court. To qualify for the ballot by petition, statewide candidates must gather 1,500 signatures from registered members of their political party in each of Colorado’s seven congressional districts. Robinson submitted 2,092 signatures from the 2nd Congressional District, which stretches from Boulder north to Fort Collins and west toward Steamboat Springs.