President Obama campaigned on behalf of Democratic presidential nominee Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE in Nevada on Sunday, also pushing those gathered to vote for Democrats running down ballot.

“Nevada’s always close,” he told the crowd in North Las Vegas, “but that’s what makes it exciting.”

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After thanking the state for helping to elect him, praising retiring Sen. Harry Reid Harry Mason ReidThe Supreme Court vacancy — yet another congressional food fight Trump seeks to turn around campaign with Supreme Court fight On The Trail: Battle over Ginsburg replacement threatens to break Senate MORE and touting the progress made during his eight years in office, Obama launched into an attack on GOP nominee Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE.

“You’ve got a guy who proves himself unfit for this office every single day in every single way,” he said.

He also criticized Trump for claiming the election process is rigged, saying: “If this was rigged, boy it would be a really big conspiracy."

“The Republican governor is not going to rig an election for Hillary Clinton or rig an election for Catherine [Cortez Masto],” he added, referring to the Democrat running for Reid’s seat.

“We’ve got to have a Congress that is willing to make progress on the issues Americans care about,” he said, before launching an extended attack on Rep. Joe Heck, the Republican facing off against Masto.

He said Heck supported Trump when it was “politically convenient” and asked “What the heck took you so long?” to denounce the nominee. Heck dropped his support for Trump earlier this month after The Washington Post uncovered a 2005 “Access Hollywood” tape in which Trump boasts of kissing and groping women without consent.

“Too late,” Obama said. “You don’t get credit for that.”

As he criticized Heck, he asked “Nevada, what the heck?” and then led the crowd in chants of “Heck no!”

Polls show a tight race between Heck and Cortez Masto, the former Nevada attorney general in a race that Heck had been narrowly leading for months.

Clinton is ahead of Trump by nearly 5 points in the RealClearPolitics average, and the latest average for the Senate race shows Cortez Masto up by 2 points.

Heck revoking his support of Trump has set off a backlash against from Trump supporters, and he’s privately acknowledged he’s in a “very difficult situation” for no longer supporting his party’s standard-bearer.