Democratic
Arizona › Arizona State Senate · November 3, 2026 · Updated Oct 16, 2026
Arizona Legislative District 13
Projected flip: Republican-held seat, Democrats favored (71%).
O'Brien is favored to win: O'Brien wins in about 2 of every 3 simulations.
O'Brien (D)
71%
chance of winning
Willoughby (R)
29%
- Average margin
- D+3.8
- 80% of outcomes
- R+6 to D+13
- Partisan lean
- Even
- Polls
- No pollsmodel only
Projected flip: Republican-held seat, Democrats favored (76%).
O'Brien is favored to win: O'Brien wins in 3 of every 4 simulations.
O'Brien (D)
76%
chance of winning
Willoughby (R)
24%
- Average margin
- D+6.5
- 80% of outcomes
- R+6 to D+19
- Partisan lean
- Even
- Polls
- No pollsmodel only
Range of outcomes
Final margin across our simulations; the white dashes mark the middle 80%.
The candidates
Republican
Julie Willoughby
What goes into the forecast
Every ingredient's estimate of the final margin.
- National environment
- D+9.5Election Day forecast
- Arizona state offices
- +0.3Polls for governor, statewide and legislative races · details
- Environment here
- D+9.8Used by the fundamentals
- Swing reaching this office
- 58%Of a shift in the environment, from past legislative races since 2016
- Southwest adjustment
- −1.5How legislative races in the region have run against lean and environment lately
Each estimate is a margin before national and statewide uncertainty is simulated. Horizon blends polls, fundamentals and a little of the similar-places estimate, weighting each by how precise it is; Pulse uses polls and similar places only.
Fundamentals inputs
| Incumbency (+1 D, −1 R) | 0 |
| Fundraising edge (log ratio of individual money) | -0.37 |
| Elected-experience edge | -0.67 |
| First-term incumbent | 0 |
| Seat's last result vs. expectation | -3.6 |
| Incumbent's last result vs. expectation | 0 |
Polls
No public polls of this race. The forecast relies on fundamentals and on polling of similar places in the state.
The district
Lean Even: how much more Democratic or Republican than the nation it votes for president.
Presidential vote
Precinct results re-aggregated to the current district lines.
Who lives here
- Population
- 230,632
- People per km²
- 1,407
- Adults with a B.A.+
- 47%
- White, no degree
- 32%of adults
- White 56%
- Hispanic 21%
- Black 5%
- Asian 12%
- Other / multiracial 7%
American Community Survey 2020–2024, aggregated from census tracts.
Past results
Results in the same-numbered district; earlier elections may have used different lines.
2024
118,074 votes · R+6.3✓ Jd. Mesnard (R)53.1%
Sharon Lee Winters (D)46.8%
2024 President Vote in this district
121,231 two-party votes · R+1.2 · D+0.3 vs. the nation✓ Donald Trump (R)50.6%
Kamala Harris (D)49.4%
2022
93,996 votes · R+3.5✓ J D Mesnard (R)51.7%
Cynthia Hans (D)48.2%
2020 Earlier district lines
93,388 votes · Uncontested by the other party✓ Sine Kerr (R)100.0%
2020 President Vote in this district
124,608 two-party votes · D+3.2 · R+1.3 vs. the nation✓ Joe Biden (D)51.6%
Donald Trump (R)48.4%
2016 President Vote in this district
87,899 two-party votes · R+5.1 · R+7.3 vs. the nation✓ Donald Trump (R)52.6%
Hillary Clinton (D)47.4%