US Senator Chris Van Hollen, who heads the Democratic Senate campaign arm, said it was "remarkable" that Democrats were even in striking distance of capturing the Senate given the unfavourable map they faced.
"This election will decide whether we build on this extraordinary prosperity we have created", Trump told a cheering crowd in Macon, Georgia, warning that Democrats would "take a giant wrecking ball to our economy".
All 435 seats in the U.S. House are up for re-election. Another 35 USA senate seats are in play, as well as nearly 40 gubernatorial votes and the balance of power in virtually every state chamber.
Trump is throwing his political muscle behind Republican statewide candidates ahead of midterm elections that could dramatically reshape his presidency.
With the election just days away as the poll was conducted, enthusiasm was up among both parties' voters, but Democrats advantage in enthusiasm narrowed to just 4 points: 68% of Democrats and Democratic-leaning independents were enthusiastic about voting, while 64% of Republicans and Republican-leaning independents said the same.
About 7 in 10 likely voters say that when they cast a ballot on Tuesday, they'll be sending a message about President Donald Trump, and more often and not, the message those voters want to send is one of opposition.
Following the outbreak of the #MeToo movement denouncing sexual assault, and the massive women's protests against Trump, women voters and candidates will play critical roles in the first major election since Trump took power.
One of the few constants ahead of any election is the expectation setting from strategists on both sides of the aisle, who engage in an effort to shape the narrative of how the election's outcome gets covered. But in Tennessee, he couldn't help but shout out the Republican Senate candidate in Arizona, Rep. Martha McSally, who faces Democratic Rep. Kyrsten Sinema. Those voters have increasingly fled Mr Trump's Republican Party, turned off by his chaotic leadership style and xenophobic rhetoric. Blue-collar men, however, have embraced the unconventional president.
A nationwide poll released Sunday by NBC News and The Wall Street Journal details the depth of the demographic shifts. Results for the full sample have a margin of sampling error of plus or minus 3.1 percentage points, for the subset of 1,151 likely voters, it is plus or minus 3.5 percentage points.
Among white college-educated women, Democrats enjoy a 28-point advantage: 61 percent to 33 percent.
The president said his record pace of campaign rallies - 11 events in eight states in the last week alone - will make a "big difference" in as many as seven Senate races. Joe Donnelly needs strong turnout Tuesday - and in his hometown of Chicago, where Democrats hope to oust a Republican governor and several House members.
And while Obama said Democrats would support a "kinder version of America", he did what many Democratic candidates have refrained from doing: directly challenging the president. "But it'll be a start".
In the final stages of the campaign, Trump has ramped up his hard-line rhetoric on immigration and cultural issues including warnings about a caravan of migrants headed to the border with Mexico and of liberal "mobs". 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.