Democrat Mike Johnston on Wednesday will be the first Colorado gubernatorial candidate to submit nominating petitions, his campaign said. The former state senator from Denver plans to turn in roughly twice the number of signatures required to qualify for the June primary ballot.

Johnston, one of five leading Democrats running for the office held by term-limited Democratic Gov. John Hickenlooper, also plans to go through the caucus and assembly process, a campaign spokeswoman told Colorado Politics.

In an unusual move for a statewide candidate, a spokeswoman said Johnston’s campaign relied entirely on campaign staff and volunteers, rather than hiring a firm, to gather the more than 20,000 signatures it plans to deliver to the secretary of state’s office Wednesday morning.

To make the June 26 primary ballot by petition, statewide candidates – include those running for governor, attorney general and state treasurer – have to collect 1,500 valid signatures from fellow party members in each of Colorado’s seven congressional districts, for a total of 10,500.

“We rolled up our sleeves and got to work for the people of Colorado,” Johnston said in a written statement. “Each signature we gathered is the product of a meaningful connection between one of our dedicated volunteers and a real-life voter. Even the conversations that didn’t yield a signature help us to see places of common ground. Gathering petitions isn’t just about getting on the ballot; it’s yet another opportunity to listen to voters and share our vision for the future of Colorado.”

His campaign said Johnston’s “army of volunteers” contacted 50,000 voters during the petition drive, which started Jan. 16.

Petitioners have until March 20 to turn in signatures to state officials.

Only one other candidate – Republican congressional candidate Darryl Glenn – has turned in petitions so far, according to election officials. That’s out of a record 59 candidates who have had petitions approved for Congress and state-level offices, from state representative to governor, the secretary of state’s office said.

Three other Democrats running for governor – U.S. Rep. Jared Polis, Lt. Gov. Donna Lynne and plastics manufacturer Noel Ginsburg – are attempting to petition onto the ballot, and two of them – Polis and Ginsburg – say they also plan to go through the caucus and assembly process. Former State Treasurer Cary Kennedy is the only leading Democratic candidate hoping to get on the ballot strictly through caucuses and assembly.

It can make a difference if a candidate turns in their petitions ahead of their primary rivals. State law only allows a voter to sign one nominating petition for each office, and the secretary of state counts signatures in the order candidates submit them, not in the order a voter signs petitions. If a voter puts a John Hancock on both Johnston’s and Lynne’s petitions, for example, it’ll count for Johnston but not for Lynne.

Johnston last month left open the possibility he might try both routes but hadn’t declared his intentions publicly until this week.

Candidates can also qualify for the primary by winning the votes of at least 30 percent of assembly delegates, a process that kicks off at precinct caucuses March 6 and culminates for gubernatorial hopefuls at the parties’ state assemblies on April 14 – the Democrats in Broomfield and the Republicans up the turnpike in Boulder.

While the top vote-getter at assembly gets top-line on the primary ballot, going both ways also carries risks. If a candidate falls below 10-percent support at assembly, that means he or she can’t qualify for the ballot by petition, in addition to falling short of the required threshold at assembly, ending his or her campaign.

Ginsburg announced a week ago he was also planning to go through assembly, on top of seeking the ballot via the petitions he’s been circulating for the past month. His campaign manager told Colorado Politics Tuesday that Ginsburg is on track to submit his petitions by mid-March, a week or so before the deadline. A spokeswoman for the Polis campaign said she wasn’t sure when his petitions would be turned in, and Lynne’s campaign manager didn’t respond to a request for comment.

At last count, 10 Republicans were running for governor, including three leading candidates who are petitioning – State Treasurer Walker Stapleton, businessman and former state lawmaker Victor Mitchell, and former investment banker Doug Robinson, one of Mitt Romney’s nephews – and several who are taking their chances with caucuses and assembly. Attorney General Cynthia Coffman said last week she was switching from petitioning to pursuing a spot on the ballot via assembly.