There's a notable absence from the "unity rally" Sen. Michael Bennet (D-Colo.) and his primary challenger, Andrew Romanoff, are both slated to attend Thursday afternoon in Denver.

The party includes appearances from Democratic National Committee Chairman Tim Kaine, Sen. Mark Udall (D-Colo.) and Rep. Ed Perlmutter (D-Colo.), who faces Republican Ryan Frazier in November.

But Denver Mayor John Hickenlooper, the Democratic gubernatorial nominee, won't be at the event, the Denver Post noted.

Hickenlooper is instead on a long-planned family vacation, a spokesman said.

He probably has the least to gain from associating himself with the national party. As Georgia Democrat Roy Barnes so aptly put it recently, "I'm not running for governor of Washington, D.C. I'm running for governor of Georgia."