The field of Republicans vying to unseat Democratic US Senator Elizabeth Warren just got smaller.

Entrepreneur Shiva Ayyadurai, who had been campaigning as a Republican, announced Saturday that he planned to run as an independent.

“We dumped the Republican Party in Massachusetts,’’ Ayyadurai said in a telephone interview. “We’ve declared our independence.’’

He made the announcement during a campaign event at a hotel in Marlborough.

Ayyadurai, who had registered as a Republican earlier this year, had been facing a primary challenge from three candidates: wealthy businessman and Republican donor John Kingston, state Representative Geoff Diehl, and longtime party operative Beth Lindstrom.

Ayyadurai, 53, of Belmont, said he plans to change his party affiliation to unenrolled. He backed Donald Trump in 2016. His campaign is focused on creating better jobs, promoting a direct-pay health care system, and reforming campaign finance, Ayyadurai said.

As of Sept. 30, Ayyadurai’s campaign had about $75,000 on hand, records show. He has raised nearly $1.3 million, much of which he financed himself.

Laura Crimaldi can be reached at laura.crimaldi@globe.com. Follow her on Twitter @lauracrimaldi.