President Trump held a Tuesday night rally in Council Bluffs, Iowa – the latest stop in the president’s busy tour boosting GOP candidates ahead of next month’s midterm elections.

He began by announcing a decision to remove a federal ban on summer sales of gasoline with high-ethanol blends, thus permitting year-round sales of gasoline with 15 percent ethanol or E15.

"We’re going with E15 year round. I made that promise to you during the campaign. I made that promise to you during the primaries," he said. "Promises made, promises kept."

The move is seen as particularly helpful for Iowa and other farm states. The summer ban was linked to concerns E15 contributes too strongly to smog. Supporters of ethanol have said the claim is unfounded.

Trump spent the majority of the rally, however, slamming Democrats while urging attendees to vote for Republicans. "The Democrats have become totally unhinged," he said. "They’ve gone crazy."

"If you want to drain the swamp, you must defeat the Democrats," he added. "This election is about security and it’s also about prosperity," he said, later claiming that "Democrats are the party of crime. Republicans are the party of safety."

Trump continued, "The only reason to vote Democrat is if you are tired of winning."

While largely focused on criticizing the Democrats, the president also recognized Iowa Sen. Chuck Grassley, the Senate Judiciary Committee chairman who recently helped push through the confirmation of Trump nominee Brett Kavanaugh to the Supreme Court. Grassley, Trump said, is a "very tough cookie."

Kavanaugh, confirmed Saturday in a 50-48 vote, had his first full day on the bench on Tuesday.

It's been a "truly historic week for America and you know what I’m talking about," Trump said, claiming the Democrats tried to ruin Kavanaugh personally. "They want to destroy everything," he said. "That’s all their good at. What the Democrats did to Brett and his beautiful family is a national embarrassment and a national disgrace."

The president said Americans need to vote on Nov. 6 to avoid the Democrats' "politics of anger and destruction."

"Never forget that in 2016 we had the greatest movement in the history of our country," he said to cheers. "With your vote, you can do so much."

The Associated Press contributed to this report.