It’s the other factors that push the race toward toss-up status, however. When a challenger has previously held an elected office, they tend to perform better with each level higher that office is. To run for Senate, O’Rourke is giving up his seat in the U.S. House, which is a higher office than had been held by Cruz’s 2012 opponent, Paul Sadler, a former state representative. Strong incumbents tend to deter strong challengers from entering the race, but Cruz wasn’t able to do so this time. Cruz also has a very conservative voting record, one that is perhaps “too conservative” even for Texas. The model actually penalizes O’Rourke slightly for his DUI scandal, but because the scandal has been public knowledge for a long time, the model discounts its importance.

Fundraising is another influential factor hurting Cruz. Ordinarily, you’d expect an incumbent to have a pretty healthy fundraising advantage. Instead, O’Rourke had more than doubled Cruz in dollars raised from individual contributors as of the end of the last filing period on June 30 — an advantage that will probably only increase once the campaigns file their next fundraising reports, which will cover up through Sept. 30. (Our model considers money raised from individual contributors only — not PACs, parties or self-funding.) If fundraising were even, Cruz would still lead in our fundamentals calculation by 4 percentage points, but O’Rourke’s money advantage is enough to bring the overall fundamentals forecast to a dead heat.