WASHINGTON — President Trump and the Republican National Committee filed a pair of lawsuits on Tuesday against officials in California challenging a new law requiring presidential candidates to release five years of tax returns in order to be placed on the state primary ballot in 2020.

The R.N.C. suit, which was filed in the Eastern District of California and included the California Republican Party and several California Republican voters as plaintiffs, called the law a “naked political attack against the sitting president of the United States.” It was filed against Gov. Gavin Newsom and the California secretary of state.

Mr. Trump and his campaign filed a second suit challenging the constitutionality of the new law, and it named the California secretary of state and the state attorney general. In that suit, they argue that states do not have the power to “supplement” the qualifications for the president, set forth by the Constitution.

The California law, known as the Presidential Tax Transparency and Accountability Act, was signed by Mr. Newsom last week, and was the latest flash point between the White House and the State of California, which is involved in more than 40 lawsuits against the Trump administration, on issues including environmental regulation and immigration.