Leaving office January 1, 2027.Did not run for re-election in 2026. This page switches to the former-officeholder layout when the term ends.

RepublicanIn office until January 1, 2027

Mark Baisley

Colorado State Senator, District 4 since 2022. Did not run for re-election in 2026; leaves office in January 2027. Lost the 2026 race for U.S. Senate in Colorado.

Colorado State Senator, District 4Born 1955Engineer

Official website Wikipedia FEC filings

In office: 3 yrs; Since 2022
Bills became law: 17; 43 sponsored, 2025–2026 session
Votes missed: 1.6%; Chamber median 1.3%
With party: 96%; On votes splitting the parties
Last margin: −25.3; Lost 2026

Source: Wikidata, congress-legislators and Open States; 99chambers legislative recordsUpdated Oct 27, 2026, 11:01 PM ET

Committees

As of 2026-10.

Artificial Intelligence Impact Task Force
Local Government and Housing
Pension Review Commission
Technology
Transportation Legislation Review
Transportation and Energy

Source: Open States committeesUpdated Oct 27, 2026, 9:43 AM ET

Legislation

2025–2026 session · 43 sponsored · 17 became law

BillIntroCmteSenateHouseLaw

HB 1250 Procedures Related to Civil Asset Forfeiture
Civil Law · Became law Jun 2026

SB 186 Update Workers' Compensation Statutes Allow Electronic Filing
Labor & Employment · Became law Jun 2026

SB 185 Enhance Security of Office of Information Technology
Telecommunications & Information Technology · Became law Jun 2026

HB 1230 Extend Conservation Easement Tax Credit
Fiscal Policy & Taxes · Became law Jun 2026

SB 189 Automated Decision-Making Technology
Labor & Employment · Became law May 2026

Source: Open States billsUpdated Nov 6, 2026, 4:22 PM ET

Voting record

2025–2026 session · placement by roll-call votes

Where Baisley sits in the Colorado State Senate

Baisley is closer to the center than 8% of the chamber's Republicans.

Closest: Lynda Zamora Wilson, John Carson, Rod Pelton

Source: 99chambers roll-call scalingUpdated Nov 6, 2026, 4:47 PM ET

With Baisley’s party

Votes with the chamber's Republicans96%
Cosponsorships of the other party's bills89%

Black tick: the average of Republicans in the Colorado State Senate.

Source: 99chambers legislative scores from roll calls and cosponsorships

Key votes

Votes chosen for their effect, not their side: Baisley’s vote, each party’s majority, and the result. An orange vote differs from most Republicans.

Date	Bill	Baisley	Rep. majority	Dem. majority	Result
May 13, 2026	SB 115: Post-Conviction Relief for Certain Offenders	No	No	Yes	Passed 18–17
May 13, 2026	HB 1274: State Agency Payments to Grant Recipients	No	No	Yes	Passed 18–17
May 13, 2026	SB 131: Sports Betting Protections	No	No	Yes	Passed 20–15
May 13, 2026	HB 1255: Social Media Duty to Report & Search Warrants	No	No	Yes	Passed 18–17
May 13, 2026	HB 1418: Online Add-on Transaction Fee Youth Service Enterprise	No	No	Yes	Passed 18–17

Source: 99chambers key votes from Congress.gov, Voteview and Open States roll calls

Career

Offices held, and every time Baisley was on a ballot. Filled marks are general elections won; hollow marks are primaries; an orange outline is a loss.

20182019202020212022202320242025202620272028Colorado House of Representatives, District 39 Colorado State Senate, District 4

Source: 99chambers results archive (MEDSL, Klarner, state election offices)

Elections

Margin against the seat’s presidential baseline: how the seat voted for president in the same or nearest year.

Year	Race	Result	Margin	Seat	+/−
2026	U.S. Senate in Colorado	Lost	D+25.3	D+11.3	−14.0
2022	Colorado State Senate, District 4	Won	R+21.7	—	—
2020	Colorado House of Representatives, District 39	Won	R+29.1	—	—
2018	Colorado House of Representatives, District 39	Won	R+28.0	—	—