Obama: 'Stop Whining,' Trump

President Barack Obama on Tuesday cast Donald Trump's claims of a rigged election as potentially corrosive to American democracy, insisting that the Republican presidential nominee was griping about an invented conspiracy.

"You start whining before the game's even over?" Obama said during a news conference in the White House Rose Garden, adding that Trump's claim is "not based on facts."

Trump and his surrogates have increasingly claimed the US election system is "rigged," coming after two lackluster debate performances and a drop in poll numbers nationally and in key swing states. He's urged his supporters to monitor polling sites for potentially ineligible voters attempting to cast ballots.

The rhetoric has been brushed off even by Republican governors, who say there are no signs of corruption in their states' voting systems.

Obama echoed those sentiments Tuesday, saying there's "no serious person out there who would suggest somehow that you could even rig America's elections."

And he claimed Trump's warnings could abrade faith in the US political system.

"One way of weakening America and making it less great is if you start betraying those basic American traditions that have been bipartisan and have helped to hold together this Democracy now for well over two centuries," Obama said.

He derided Trump's remarks as reflective of an unpresidential attitude, declaring again that the Republican nominee's temperament was disqualifying.

"It doesn't really show the kind of leadership and toughness that you'd want out of a president. You start whining before the game's even over? If whenever things are going badly for you and you lose you start blaming somebody else? Then you don't have what it takes to be in this job," Obama said.

And he said the warnings of a "rigged election" are entirely unprecedented in modern American political history.

"I have never seen in my lifetime or in modern political history any presidential candidate trying to discredit the elections and the election process before votes have even taken place. It's unprecedented," Obama said alongside Italian Prime Minister Matteo Renzi.

Trump has at times embraced the label of "whiner," telling CNN in an interview last year, he is "the most fabulous whiner."

"I do whine because I want to win and I'm not happy about not winning and I am a whiner and I keep whining and whining until I win," Trump told CNN's Chris Cuomo in August 2015.

(CNN)