Though President Trump is not personally up for election, his administration faces its first big nationwide test of American public opinion tomorrow.
Trump has seized on the nativist us-versus-them message that resonated with his base during the fiery 2016 campaign as he races across the country to secure votes, using inflammatory language as he paints a country under threat from hordes of illegal immigrants, rampant crime and far-left Democrats. "And they want to erase America's borders", Trump told a raucous rally in Chattanooga, Tennessee late Sunday. Now 235 are held by the Republicans and 193 by the Democrats with seven vacancies due to deaths.
Most midterm elections, business-oriented Republican fund-raising efforts far outpace those of Democrats, generally fuelled by labour and other interest groups.
Mr Biden, who was campaigning in a tight congressional race in conservative central Pennsylvania, urged people to vote Democrat in tomorrow's election.
Voters on Tuesday will decide the $5 billion debate between President Donald Trump's take-no-prisoner politics and the Democratic Party's super-charged campaign to end the GOP's monopoly in Washington and statehouses across the nation.
Evidence of this love and respect towards Obama gave was clearly visible during his address in support of senator Bill Nelson and gubernatorial candidate Andrew Gillum.
Trump has been beating the drum against a caravan of migrants from Central America that is vending its way through Mexico to the USA border. Worries about foreign interference are more widespread among Democrats, 74% of whom think it's likely to happen and 90% of whom consider it a major problem.
It did not take long for the video to go viral, with many praising the former president.
"The level of fervor, the level of fever is very strong in the Republican side", said Trump, adding: "I have never seen such excitement". "There is a lot of energy out there".
That is the worst pre-election approval rating for any president approaching their first midterm election in polling dating back to Eisenhower.
White women without college degrees prefer Republicans by a 12-point margin, though white women with degrees clearly prefer Democrats, 61 percent to 33 percent. The party's 55% to 42% advantage in the new poll mirrors their lead in early October and is about the same as the 10-point edge they held just after Labor Day.
If the Democrats have to gain control, they have to win 40 seats more than what they did in the last mid-term poll in 2014.
A fanatical Trump supporter was also arrested on charges of mailing pipe bombs to prominent opponents of the president, including Obama. "But I have never seen such an enthusiastic Republican Party".
But the president - to the unease of some in the party - has instead used his almost nonstop schedule of campaign rallies to keep the spotlight on what he calls the security threat from migrants seeking to enter the United States through Mexico.
Trump is complaining at a rally in Georgia that "we pay these countries hundreds of millions of dollars" even though "they don't do a damn thing for us".
That would allow them to keep the ability to approve "U.S".
Obama meanwhile did what many Democratic candidates have refrained from doing: directly challenging the president.
"When words don't mean anything, when truth doesn't matter, when people can just lie with abandon, democracy can't work", he said.
"The only check right now on the behaviour of these Republicans is you and your vote", Obama told supporters in Gary, Indiana, during a rally for endangered Democratic Senator Joe Donnelly.
Another 28% say their vote isn't about the president.