President Obama is turning his attention to the Senate as he barnstorms in key battleground states during the final stretch of the 2016 campaign.

Obama has unleashed a torrent of criticism on Republican senators in Ohio, Florida and Nevada, tying them to Republican presidential 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 whether they have disavowed him or not.

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Obama traveled to Miami last Thursday with the express purpose of campaigning for Democratic 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. But he saved his toughest words for Florida Sen. Marco Rubio Marco Antonio RubioOvernight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers Democrats step up hardball tactics as Supreme Court fight heats up Press: Notorious RBG vs Notorious GOP MORE, blasting him for sticking by Trump even though he had called the businessman a “dangerous con artist” during their vicious GOP primary fight.

On Sunday in Las Vegas, Obama said Rep. Joe Heck (R), who is running for retiring Senate Minority Leader 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’s (D) seat, doesn’t deserve credit for abandoning Trump, especially since he told donors behind closed doors he “really” wants to support him.

“So how does that work?” Obama asked incredulously. “You're for him, but you're not for him. But you’re kind of for him. What the heck?”

Later this week, Obama will make a return trip to Florida, where he’s expected to boost both Clinton and Rubio’s challenger, Rep. Patrick Murphy (D). Democrats need to net five seats to win back control of the upper chamber, or four if they retain the White House.

The president has long faced criticism from Democrats that he has not done enough to help congressional candidates.

Since Obama became president in 2009, Democrats have lost 11 governorships, 13 Senate seats, 69 House seats and more than 900 state legislature seats, according to an analysis conducted by the University of Virginia Center for Politics.

As a result, the fourth-quarter effort is a touchstone on Obama’s legacy. Significant gains could help save face for a president who has seen a lot of Democratic officeholders go down to defeat during his presidency.

“Obama had the worst down-ballot record of any post-World War II president in terms of the overall losses his party suffered,” said Geoffrey Skelley, political analyst at the Center for Politics.

“He is criticized at times during his presidency for not spending as much time thinking about the party as a whole,” Skelley added.

Bitterness followed when Democrats lost the Senate in 2014. On the night of that midterm election, biting comments directed at Obama from Reid’s then-chief of staff David Krone showed up in The Washington Post.

Krone appeared to blame the president for the loss of the Senate.

“The president’s approval rating is barely 40 percent,” Krone said. “What else more is there to say?”

He accused Obama of paying “lip service” to efforts to keep the Senate in Democratic hands after the 2014 election and said Obama did not do enough to fundraise for the Senate Majority PAC, an outside group.

In 2016, Senate Democrats are getting a different Obama.

Obama is raising money for the Senate Democrats on Tuesday at a Los Angeles fundraiser, one of 16 such events he’s headlined this cycle, according to a Democratic official.

The president is appearing in television ads for five Senate candidates: Murphy, California’s Kamala Harris, Illinois Rep. Tammy Duckworth, North Carolina’s Deborah Ross and Katie McGinty of Pennsylvania.

He’s also cutting radio spots for Gov. Maggie Hassan of New Hampshire, Heck opponent Catherine Cortez Masto, Murphy, Ross and McGinty.

The Cortez Masto campaign filmed Sunday’s rally with Obama to turn it into a TV ad, according to spokesperson Kristen Orthman.

Obama on Monday endorsed 30 more House candidates, trying to aid the party’s long-shot bid to retake the lower chamber. He’s cut radio or TV ads for 10 House hopefuls. He’s also publicly backing 150 state legislative candidates, a Democratic official said.

Without his name on the ballot on Nov. 8, Obama has seemed to relish letting loose on GOP officeholders who have stymied his agenda for years.

The enthusiasm he’s shown in going after Republicans down the ballot is something longtime Democratic observers see as a change.

“In years past, I think House and Senate Dems had reason to express concern that the president wasn’t doing enough to do help down-ballot races,” said Democratic strategist Jim Manley, a former top aide to Reid. “When Harry Reid and Pelosi went down to the White House, they would normally be given about half of what they’re asking for.”

“But it sure doesn’t look like the case this time,” Manley added.

White House officials have long said the president has done what’s asked of him by congressional Democrats.

They argue that Democrats down ballot largely turned away from Obama in the 2010 and 2014 midterms, when the president was unpopular.

The circumstances are different this year. Obama’s strong approval rating means he’s a hot commodity for Democratic office-seekers. The Senate map and presidential-year demographics also favor Democrats.

Regardless, party members acknowledge Obama is putting a bigger premium on down-ballot races than he has in the past.

“The scope of this effort ... is unusual,” said one Democratic official. “There has definitely been a strategic choice to be out there strongly for Democratic candidates up and down the ticket.”

The push is also important for Clinton, who desperately wants a Democratic Senate in order to advance her agenda during her first two years in office if she wins.

Democrats are feeling a sense of urgency about regaining control of the Senate this year. The map turns in the Republicans favor in 2018, when Democrats have to defend 25 seats, including five in traditionally red states.

“We can't elect Hillary and then saddle her with a Congress that is do-nothing, won't even try to do something, won't even get their own stuff passed, much less the stuff you want passed,” Obama said Sunday night in Las Vegas.

"We’ve got to have a Congress that’s willing to make progress on the issues Americans care about.”

Jordain Carney contributed.