Trump campaigned with Georgia Secretary of State Brian Kemp, who is in a tight and controversial race with Democrat Stacey Abrams for the governor's office.
But two years after an election that proved polls and prognosticators wrong, nothing is certain on the eve of the first nationwide elections of the Trump presidency.
Without naming the current United States leader, Mr Obama condemned him and Republicans for what he described as divisive policies.
He criticised Republicans for trying to repeal Obamacare while claiming to support the healthcare law's protections for those with pre-existing conditions.
"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.
Ms. Trump, senior adviser to the president's 2020 campaign, said on Saturday that Democrats are scared because of Trump's results. If Trump manages to pull off a victory in terms of retaining control of one or both Houses, it will be seen as a validation of his stand that poor migrants and refugees from other countries are a threat to the peaceful life of the American people and send out a clear message to the world on what the original "country of migrants" now thinks on that issue. The midterm elections involve all 435 seats of the House of Representatives, 35 of the 100 seats in the Senate, and 36 out of 50 state governors. Majorities in both parties say he's extremely important to their vote (55% of Republicans, 53% of Democrats).
On Tuesday, US voters will decide between President Donald Trump's take-no-prisoners rhetoric and the Democratic Party's super-charged campaign to end the Republicans' monopoly in Washington and state legislatures across the nation.
He told supporters to "look at what is marching up - that's an invasion".
Premier League pays tribute to Leicester owner Vichai Srivaddhanaprabha
Leicester's players had worn white T-shirts bearing Vichai's image and the words "The Boss" during the pre-match warm-up. Leicester City's players travelled to Bangkok to attend Vichai's funeral after their match with Cardiff City last night.
Most Democrats consider the Russian Federation investigation a critical part of their vote (53% say it's extremely important), but just 8% of Republicans say the same.
On Friday, the Labor Department's monthly employment report produced a string of positive numbers: another month with the unemployment rate at 3.7 percent, the lowest in half a century; 250,000 jobs added to the workforce; and wages posting the biggest increase in nearly a decade and faster than inflation.
And he's crediting the dozens of rallies he's held on behalf of candidates, saying that they "have really been the thing that's caused this big fervor" to start and to continue.
The gender gap cuts across lines of race and education, with non-white women (79% favor Democrats) and white women with college degrees (68% back the Democrat) breaking most heavily for the Democrats, while white men (57% Republican) and particularly white men without college degrees (65% back the Republican) are most deeply behind the GOP.
Their appearances on the campaign trail are considered effective because Trump and Obama are regarded as the most popular figures in their parties.
Speaker of the House Paul Ryan (R-WI) appealed to President Trump in a phone call on Monday, begging the President to focus his rhetoric a bit more on the economy and a bit less on immigration, Politico reported.
"The fact we still have a narrow path to a majority is a sea change from where we were two years ago", he said on ABC.
Mr Trump has delivered a very different closing argument, railing against Latin American immigrants seeking asylum at the USA border. Around 37 percent of eligible voters took part in the 2014 midterm elections, down from 42 percent in 2010.