[2] He is the third of ten children of Tomas and Celina Vargas, who immigrated to the United States from Mexico in the late 1940s as part of the Bracero program.

[citation needed] He left that job at the end of 2009 to run as a Democratic candidate for the California State Senate.

In 2010, Vargas narrowly won a seat in the California's 40th State Senate district, defeating Assemblywoman Mary Salas by 22 votes after recounts in San Diego and Riverside counties.

[20] In 2012, when Filner announced he would retire from Congress to run for mayor of San Diego, Vargas endorsed him despite their history of bitter rivalry.

Republican Michael Crimmins ranked second with 20%, Democratic state senator Denise Moreno Ducheny third with 15%, and four other candidates received single-digit percentages.

[25][26] In 2019, Vargas spent $124,200 of campaign money on photography, printing, postage, mailing and shipping of holiday cards that he sent to constituents.

Part of Vargas's congressional work, the trip was to help him develop "a greater understanding of the key legislative topics of the 114th Congress through our [Germany and the United States] transatlantic relationship.

"[28] In 2022, Vargas was one of 16 Democrats to vote against the Merger Filing Fee Modernization Act of 2022, an antitrust package that would crack down on corporations for anti-competitive behavior.

[29][30] He voted in favor of a bill that provided an additional $14.3 billion to support Israeli military operations in the Gaza Strip.

[38][39] He opposed the overturning of Roe v. Wade, calling it "fundamentally wrong and extremely disappointing, impacting millions of women across the country.

[43] In February 2025, Vargas joined a protest against Donald Trump's immigration policies led by religious leaders including Cardinal Robert McElroy, the Bishop of San Diego and Archibishop-elect of the Archdiocese of Washington.