Published: Thursday, Oct. 9, 2014 - 4:32 pm

Two years ago, Democrats won what were quickly dubbed “supermajorities” in both houses of the Legislature, but in the ensuing months, they lost the Senate supermajority.

When a Democratic incumbent resigned in 2013 to become a corporate executive, Republicans won the seat in a special election. And this year, three Democratic senators facing felony charges were suspended.

Those incidents dropped the Democrats from 29 seats to 25, two short of the 27 needed to pass measures requiring two-thirds votes such as constitutional amendments, urgency statutes and tax increases.

It played a role in the drafting of a $7.5 billion water bond for the Nov. 4 ballot. By maintaining solidarity, Republican senators were able to secure more money for new reservoirs.

It also stalled once-ambitious tax increase plans of some Democrats.

The biggest election issue this year, at least among Capitol insiders, is whether Democrats can regain their supermajority in the Senate and hold their 55-seat supermajority, now just one over the two-thirds mark, in the Assembly.

The latter appears to be the more likely. While two Democrats who won in conservative Assembly districts in 2012, Steve Fox of Palmdale and Sharon Quirk-Silva of Fullerton face serious challenges, Republicans also have a seat or two at risk, so the net outcome could be a wash.

The prospects for Democrats to regain a supermajority in the Senate appear to be dimmer and very likely will boil down to what happens in Orange County’s 34th Senate District, which was heavily redrawn by the state’s independent redistricting commission, becoming less Democratic and thus potentially winnable by a Republican.

Janet Nguyen, a Republican county supervisor, and Jose Solorio, a former Democratic assemblyman, are the candidates, and both parties are pouring money and other resources into the Santa Ana-centered district. Gov. Jerry Brown is even making a rare effort to prop up Solorio.

The rivals met in a debate recently and it revealed the underlying stakes.

Two years ago, as Democrats were winning their supermajorities, voters approved temporary increases in sales taxes on everyone and income taxes on the rich. Were the supermajorities to reappear, labor unions and other liberal groups hope they would extend the taxes and perhaps add an oil severance tax or other new levies to the revenue mix.

However, when the tax issue arose in the debate, Solorio, mindful that the 34th SD has changed, declared that he wouldn’t vote for a tax extension.

Other Democratic candidates in tough races are also shunning support for a legislative tax hike, meaning pro-tax groups such as the California Teachers Association probably cannot look to the Legislature and must spend millions on another ballot battle in 2016.