The conflict-of-interest rules for a commission that will rule on campaign finance violations in races for key county offices were strengthened this week.

ROB VARELA/THE STAR Matthew Becerra votes at Tierra Vista Elementary School in Oxnard Tuesday.

Earlier this year, county supervisors decided that commissioners must recuse themselves if they have ever made a contribution for or against a candidate in a case that comes before the panel. The rule also applies to the commissioners’ spouses.

On Tuesday supervisors…