Voting is still open until April 28 for those who haven't cast a ballot in the Ohio primary, but it's mail-in only. Ohio officials say the process is safe and secure, striking a contrast to President Donald Trump's recent comments.

Trump called mail-in voting "horrible" and "corrupt," saying there's a "tremendous potential for voter fraud."

"Republicans should fight very hard when it comes to state wide mail-in voting," Trump wrote. "Democrats are clamoring for it. Tremendous potential for voter fraud, and for whatever reason, doesn’t work out well for Republicans."

Ohio's extended election was approved unanimously by the GOP-controlled legislature, and signed into law by a Republican governor.

Gov. Mike DeWine says he hasn't heard the president's comments but says Ohio's vote-by-mail process is safe, especially compared to the risks of voting in-person.

"You know, we postponed the election, or we expanded the election basically, because we didn't think it was safe, but yes, it's safe for people to vote in Ohio and we're asking them to do that," DeWine said at his press conference Wednesday.

State elections officials have consistently said that voter fraud is rare.

"Though we are preparing for every possible scenario, our expectation and hope is that we’ll be able to have a normal election in November," said Maggie Sheehan, spokesperson for Secretary of State Frank LaRose, issued a written statemen. "That said, it's fortunate that Ohio has a long history of running secure elections, and that includes decades of voting by mail. From voter-specific ballot tracking and frequently maintained voter rolls to security measures at county boards of elections where ballots are handled and stored by a bipartisan team of election officials, Ohioans can be confident that their vote-by-mail ballots are as safe and secure as the votes cast on Election Day."

The primary was extended after state officials closed the polls on March 17, fearing the large groups would increase the spread of coronavirus.

Voters can cast their absentee ballot by mail with a postmark date of April 27, or drop it off at their local board of elections by April 28.