Ordinarily, a special legislative election in a rural corner of California would not generate much outside interest.

But the May 21 election to fill a state Senate vacancy in the southern San Joaquin Valley is getting a lot of attention because its outcome is in doubt. Were the Republican to win, it could imperil the Democrats' supermajority in the Senate, especially because Republicans are expected to pick up one or two Senate seats in the 2014 regular election.

The vacancy was created when Democrat Michael Rubio of East Bakersfield resigned midway through his first Senate term to work for Chevron. But because Rubio was elected in the 16th Senate District in 2010 – before Senate districts were redrawn – the special election to fill his seat must be conducted in the old district.

That district has about an 18-percentage-point Democratic registration advantage, which would favor the anointed Democratic candidate, Kern County Supervisor Leticia Perez. And her position strengthened markedly this week when another Democrat, Fran Florez, dropped out.

Florez, whose son, Dean, was Rubio's predecessor, clearly was under pressure from party leaders to step aside. They worried that a Perez-Florez duel would consume money, generate discord and give the GOP candidate, Hanford farmer Andy Vidak, a better shot. Vidak, who is well known in the region, made a strong bid for Congress in 2010.

The advantage that Perez gains from Florez's departure, however, does not make her a shoo-in.

She's a newcomer to electoral politics, having served only a few months as a Kern supervisor, she was forced to change residences to run for the Senate, Kern has just a quarter of the 16th District's voters, she's little-known in the much larger Fresno-Tulare-Kings county portion, and there's some local resentment about abandoning her county position so quickly.

Finally, as with all special elections, there's voter turnout.

A similar election was conducted recently in a heavily Latino Southern California Senate district and just 9.15 percent of registered voters cast ballots. The makeup of the 16th Senate District – with large numbers of relatively poor Latino Democrats – virtually guarantees a very low voter turnout on May 21.

Vidak, meanwhile, will have strong agricultural support and, from early fundraising numbers, no shortage of financing to counter the money that the Democratic Party and its allies, especially unions, will pour into Perez's campaign.

He's likely, too, to make the bullet train project a major issue. Its route cuts through the heart of the district, it's very unpopular, and Rubio, Perez's mentor, provided a key Senate vote for it.

All in all, Perez still has the advantage, but it shapes up as a very hard-fought contest with an uncertain outcome.

Call The Bee's Dan Walters, (916) 321-1195. Back columns, www.sacbee.com/walters. Follow him on Twitter @WaltersBee.

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