Denver Health spent much of the last year laying the groundwork for a proposed sales tax increase that its leaders see as crucial for shoring up the system’s long-strained budget. But just as the Denver City Council was considering sending that tax to the ballot in June, news emerged that Mayor Mike Johnston was teeing up an even bigger ask for voters: a new dedicated sales tax — the largest in city history — to pay for his affordable housing initiatives. Now both are on Denver’s November ballot, and if both pass they would add a combined 0.84 percentage points to the city’s effective 8.81% sales tax rate — pushing it to 9.65%, among the higher rates in the state.