One of the Bay Area's most-watched congressional races got a lot more crowded by Friday's candidacy filing deadline.

The challenge to Rep. Mike Honda, D-San Jose, from well-funded fellow Democrat Ro Khanna of Fremont has been making national headlines since last April.

Dr. Vanila Singh, a Republican from Fremont, entered the 17th Congressional District race in January. But two other candidates completed their filings by Friday's 5 p.m. deadline: Google attorney Vinesh Singh Rathore, an independent from San Jose, and tech recruiting executive Joel Vanlandingham, a Republican from San Jose. That could be bad news for Khanna, whose strategy includes appealing to voters across party lines.

A similar 11th-hour curve ball came in the East Bay's 15th Congressional District, where freshman incumbent Rep. Eric Swalwell, D-Pleasanton, is being challenged not only by fellow Democrat and state Senate Majority Leader Ellen Corbett of San Leandro as expected, but also by Alameda County Republican Party vice chairman Hugh Bussell, a software development manager from Livermore.

Both districts have heavy voter-registration advantages for Democrats, but the state's "top two" primary system -- in which candidates of all parties compete directly in June's primary and the top two vote-getters advance to November, regardless of party affiliation -- means any candidate might help tip the balance in favor of another.

Candidates hoping to succeed Corbett in the 10th State Senate District include Assemblyman Bob Wieckowski, D-Fremont; former Assemblywoman Mary Hayashi, a Hayward Democrat; Roman Reed, a Fremont Democrat; Peter Kuo, a Santa Clara County Republican; and Audie Bock of Hayward, who switched from Green to independent while serving in the Assembly, was later a Democrat and now is a Republican. Alameda County Superior Court Judge Roy Hashimoto took out candidacy papers for this race but did not return them by Friday.

Wieckowski's Senate bid leaves his 25th Assembly District seat up for grabs. Filing for that seat by Friday were former Fremont Police Chief Craig Steckler, San Jose Councilman Kansen Chu, Milpitas Councilman Armando Gomez and Ohlone College Trustee Teresa Cox of Fremont, all Democrats, as well as former Ohlone Trustee Bob Brunton, a Republican from Fremont.

Vying to succeed termed-out Assemblyman Paul Fong, D-Cupertino, in the 28th Assembly District are Fong aide and Campbell Mayor Evan Low and Cupertino Councilman Barry Chang, both Democrats, as well as Saratoga Councilman Chuck Page and Michael Hunsweck of Stanford, both Republicans.

In Santa Clara County, four-term incumbent Sheriff Laurie Smith faces two challengers: Capt. Kevin Jensen, a 28-year department veteran backed by the deputy sheriffs' and jail guards' unions, and former San Jose police officer Martin Monica, who failed to unseat Smith in 2000.

Supervisors Mike Wasserman and Ken Yeager, as well as the district attorney and assessor, are unopposed for re-election. But seven candidates are vying for three Santa Clara County Superior Court judicial seats.

Defense attorney Dennis Lempert and Deputy District Attorney Julianne Sylva are vying for retiring Judge Kevin McKenney's seat, while Deputy District Attorney Stuart Scott and Deputy Attorney General Ralph Sivilla both seek to replace departing Judge Gilbert Brown. And for the first time in 15 years, a judicial incumbent faces challengers: Deputy District Attorney Matt Harris and defense attorney Annrae Angel going after Judge Diane Ritchie's post. Another 26 judges are running unopposed.

In San Mateo County, two supervisors face challengers in their re-election bids.

In District 2, Carole Groom -- a supervisor since 2009 and former San Mateo mayor -- faces Mark De Paula, a retired telecommunications industry worker and disabled Vietnam-era veteran from San Mateo. And in District 3, Supervisor Don Horsley, a former county sheriff, is opposed by Michael Stogner, a perennial candidate from San Carlos who made his third unsuccessful bid for supervisor in 2011.

Assessor-County Clerk-Recorder Mark Church faces a challenge from Redwood City businessman John Mooney, and Coroner Robert Jon Foucrault faces a challenge from Redwood City small business owner Rick Dalton.

The deadline to file for the county controller's office isn't until Wednesday because incumbent Bob Adler is not seeking re-election. So far, former Burlingame mayor Joe Galligan and the county's current assistant controller, Juan Raigoza, have both qualified to run.

Superintendent of Schools Anne Campbell, District Attorney Steve Wagstaffe, Sheriff Gregory Munks and Treasurer-Tax Collector Sandie Arnott face no challengers.

Staff writers Bonnie Eslinger and Eric Kurhi contributed to this report. Contact Josh Richman at 510-208-6428 and follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics.