Photo taken in Arlington, Virginia, the United States on Sept. 29, 2020 shows C-SPAN 2 live stream of U.S. President Donald Trump (L) and his Democratic challenger Joe Biden speaking during their first debate in the 2020 presidential race. (Photo: Xinhua)

US President Donald Trump campaigned frantically and frontrunning challenger Joe Biden stayed mostly out of sight Tuesday ahead of a pivotal televised debate with only two weeks until Election Day.

The contrast in campaign strategies between Trump, 74, and Biden, 77, has never been more pronounced: The Republican president left for another rally in the battleground state of Pennsylvania, while the Democrat played it cool at his home in Delaware - though he will deploy his former boss, Barack Obama, to Philadelphia for a rally on Wednesday.

Polls show Biden ahead and with the clock running down, he appears confident.

In any case, few could ever out-campaign Trump, who has rediscovered his old energy with daily, sometimes twice-daily rallies around the country since recovering from COVID-19 just over a week ago.

His latest rally was in Erie, a former Democratic stronghold that he won in 2016, symbolizing his successful capture of the white, working class vote that had long been loyal to the left and which Biden has been trying to claw back.

Trump's message with 14 days to go has boiled down to a mix of optimism, telling Americans that the pandemic is practically over, and ever more extreme attempts to tar Biden as corrupt.

But, underlining how hard it is for him to escape the subject of the COVID-19 crisis, Trump's wife Melania canceled plans to accompany him to Pennsylvania at the last minute, complaining of ongoing discomfort following her own bout with the virus.

This was to have been her first appearance alongside Trump at a rally in more than a year, possibly boosting his dire standing among women voters.

The trip was canceled due to a "lingering cough" following her infection, a spokeswoman said.

After a difficult few weeks for his reelection hopes, compounded by three nights in hospital with coronavirus, Trump believes he is storming into the final stretch with new momentum - even if published polls show little sign to support this theory.

Both candidates will get something of a reality check on Thursday when they meet for their final televised debate.

To try and impose some sense of order after a chaotic first clash in September, the moderator will this time switch off the microphone of the candidate not meant to be speaking, thereby trying to thwart interruptions.