Secretary of State Dennis Richardson faced mounting pressure Friday from other Oregon leaders over a White House request for help with its investigation into alleged voter fraud in the 2016 presidential election.

Richardson rejected the request to hand over voter information, saying a presidential commission can get voter information the same way anyone can: by paying $500.

In a letter to Kris Kobach, the vice chair of the Presidential Advisory Commission on Election Integrity, Richardson said he “doesn’t believe the federal government should be involved in dictating how states conduct their elections.”

“We have very little evidence of voter fraud or registration fraud in Oregon,” said Richardson. “There have been 15 individuals indicted or convicted of voter fraud since 2000.”

In a letter to Richardson, a Republican, Democratic state Reps. Barbara Smith Warner and Rob Nosse had urged Richardson to reject a June 28 request for voter information by the Presidential Advisory Commission on Election Integrity. The lawmakers said it would only “serve to legitimize false claims of massive voter fraud in last November’s election.”

In another letter dated Friday, U.S. Sens. Jeff Merkley and Ron Wyden called Trump’s claims of voter fraud “nonsensical” and questioned the credentials of Kris Kobach, the Kansas secretary of state running the commission. The two Democrats note that the commission has asked states to provide the sought voter information to an insecure email address.

The commission wants publicly available voter data that could include the full names, addresses, birthdates, political affiliations and voter histories of registered voters.

In a series of tweets Thursday, Wyden urged Richardson to follow the lead of other secretaries of states who’ve denied the request, saying compliance would endanger Oregonians’ “security, privacy and right to vote.”

California Secretary of State Alex Padilla denied the commission’s request the following day, saying California’s participation would only legitimize what he calls “false and already debunked claims” of voter fraud.

The commission convened in May after President Donald Trump signed an executive order to establish the commission, which is headed by Vice President Mike Pence.

In response to the executive order, Richardson released a statement in May saying he would refuse any request to participate in the commission in order to focus on serving Oregonians.

“Oregon has an open and honest voting system,” Richardson said in the May statement. “You can’t hack paper. There will always be isolated instances of individuals acting in ways contrary to our values, but we will find them and prosecute them.”

Washington Secretary of State Kim Wyman said her office is now reviewing the White House request.

This story has been updated.