Partisan control of the Colorado Senate would depend on the outcome of races in eight toss-up districts under the latest draft legislative maps released Thursday, though Democrats would have a clear advantage in the House.

Twelve districts under the new Senate draft map would be considered safe for Democrats, while five would lean in the party’s favor. Nine districts would be considered safe for Republicans, with an additional district leaning toward the GOP.

Whichever party controls 18 seats controls the 35-member chamber, and the balance of power would be determined under the latest draft map by which party wins the toss-up districts.

Democrats currently have a 20-15 advantage in the Senate.

The legislative commission has a policy defining political competitiveness based on an average of election results from eight statewide races between 2016 and 2020. The metric looks at the difference between the percentage of votes cast for a Republican candidate versus the percentage of votes cast for a Democratic candidate.

Nonpartisan staff consider a district competitive if neither party has an advantage of more than 8.5 percentage points. The Colorado Sun considers a district competitive, but leaning in favor of a political party if it has an advantage of at least 5 percentage points.

Under the draft House map, 34 seats would be considered safely Democratic, giving the party an easy majority in the 65-member chamber.

The new maps could ultimately determine which party controls the state legislature, which has been in Democrats’ hands for the past three years. Democratic Gov. Jared Polis, who is up for reelection next year, will need his party to continue to control both chambers of the legislature to advance his agenda.

The legislative redistricting commission must submit its maps to the Colorado Supreme Court on Oct. 15. At least eight of the 12 commissioners, including at least one of the panel’s four unaffiliated members, must agree on a proposal for it to be sent to the court.

If commissioners can’t reach an agreement on a proposal by Oct. 11, the next map issued by staff — set for release Oct. 3 — will be sent to the court. That means the next two weeks will be crucial for the commission as it works to find consensus.

The fast-approaching deadlines mean the maps released Thursday, and how they are changed, are critical starting points for the final stretch.

While candidates for the U.S. House don’t need to live in the district they represent, candidates for the state legislature do. That means changes to the districts could leave some incumbents and candidates out of the running unless they’re willing to move or challenge a colleague, potentially in a primary.

The latest draft Senate map would draw at least six incumbents into the same district.

Because state law requires incumbents be able to serve their entire term, Hisey would essentially be knocked out of a seat. He would have to move into another district to run for reelection, if the map doesn’t change. Hisey cannot challenge Gardner in a primary election next year.

A similar situation would play out in Senate District 5, which would be home to both Republican Sens. Don Coram, of Montrose, and Bob Rankin, of Carbondale. Rankin was elected to a four-year term last year while Coram is up for reelection in 2022.

At least three districts — 3, 7 and 22 — would not have an incumbent under the new map. All three are considered safe Republican districts.

The eight toss-up districts that would decide control of the Senate would include Senate District 2, which is made up of part of Colorado Springs, as well as Senate District 5, which incorporates Aspen, Glenwood Springs, Montrose and Gunnison.

Other toss-up districts would include Senate District 6, which spans the San Luis Valley and counties in Colorado’s southwest corner. Senate District 21, which runs through eastern Arapahoe and Adams counties and into Brighton and the north Denver metro area, would also be a toss-up.

Because senators are elected to four-year terms, the true effect on partisan control of the Senate under the new map won’t be borne out until after the 2024 election.

At least 10 of the 65 state House districts would be home to two incumbents.

Five districts would be home to two Republican incumbents, while three districts would be home to two Democrats.

Since House members run for reelection every two years, incumbents could face each other in a primary or general election under the new map. Here’s a list of districts that would be home to two incumbents under the latest draft map:

The legislative redistricting commission has heard from Hispanic advocacy groups that their community — which represents about a quarter of the state’s population — needs more representation at the Capitol.

Sixteen of the proposed House seats would be at least 30% or more Hispanic, and 15 of those would be heavily Democratic, with the 16th leaning to Democrats. At least seven Senate seats would be at least 30% or more Hispanic.

Another eight House districts would be 11.9% to 20.5% Black, all heavily Democratic districts. Only three Senate districts would fall into that category.

What’s next

People may still share feedback about the proposed legislative map by submitting comments online.

The Legislative Commission will meet to review the new maps at 1 p.m. Friday, with another meeting at 1 p.m. Sunday.

If necessary, a third set of legislative maps will be released Oct. 3.

The Colorado Sun is a reader-supported, nonpartisan news organization dedicated to covering Colorado issues. To learn more, go to coloradosun.com.