DES MOINES, Iowa/WASHINGTON (Reuters) - U.S. Democratic presidential candidates gave a cool reception on Sunday to former New York Mayor Michael Bloomberg’s potential independent White House run, with Bernie Sanders saying it would add another billionaire like Republican Donald Trump to the race.

With eight days to go until Iowa holds the first nominating contest on the road to the Nov. 8 presidential election, Republican Senator Marco Rubio basked in the glow of an endorsement from the Des Moines Register, the state’s biggest newspaper.

The weekend disclosure from a source close to the situation that Bloomberg is laying the groundwork for a run that he could launch should Democratic front-runner Hillary Clinton falter, sent shock waves rippling through the entire presidential field.

Sanders, a democratic socialist and Vermont senator who is threatening Clinton in Iowa and New Hampshire, told ABC’s “This Week” program that Bloomberg’s entry would add a second billionaire to the field. Trump, a real estate mogul, is leading the crowded Republican field.

Sanders has railed against “millionaires and billionaires” and the political power they wield throughout his insurgent campaign for the Democratic nomination.

“That is not what, to my view, American democracy is supposed to be about, a contest between billionaires. If that takes place, I am confident that we will win it,” Sanders said.

Many analysts believe a Bloomberg entry into the race could siphon Democratic votes and be another blow to Clinton, a former secretary of state and the wife of former President Bill Clinton.

An independent bid would be a heavy lift for Bloomberg. The last major third-party candidate, Ross Perot, won 18.9 percent of the vote in 1992, which some observers believe enabled Bill Clinton to defeat President George H.W. Bush.

Hillary Clinton, who won the Register’s endorsement on the Democratic side on Saturday, said she expected to negate Bloomberg’s rationale for running.

File photo of former New York City mayor Michael Bloomberg speaking during a news conference at City Hall in New York, September 18, 2013. REUTERS/Brendan McDermid

“He’s a good friend of mine and I am going to do the best I can that I get the nomination and we’ll go from there,” she told NBC’s “Meet the Press.”

“The way I read what he said is that if I didn’t get the nomination, he would do it. ... I will relieve him of that,” she said.

Bloomberg, 73, a media magnate who has long privately flirted with the idea of a presidential run, served as mayor of New York from 2002 to 2013. He switched his party affiliation from Republican to independent in 2007 and has spent millions in recent years on national campaigns to tighten U.S. gun laws and reform immigration.

TRUMP ‘WOULD LOVE’ BLOOMBERG IN RACE

Trump noted that he and Bloomberg had differences on the issues of gun control and abortion and that he would love to run against him. Bloomberg favors preserving a woman’s right to an abortion.

“I know Michael very well and would love to compete with him. He is very opposite from me on guns and pro-life. ... I would love to have Michael get in the race,” Trump told CNN.

Former Florida Governor Jeb Bush told the ABC program that Bloomberg had been a “great mayor,” who was unlikely to get into the race unless Trump and Sanders were the parties’ nominees.

“But that’s way off into the future,” Bush said.

Rubio, at a town hall meeting in Marion, Iowa, brought up Bloomberg’s attempts for more gun control. He said he had been asked in a television interview to comment on Bloomberg’s potential candidacy.

“I said he’s not a candidate. If he gets in, we’ll talk about his record and his hatred for the Second Amendment,” Rubio said, referring to the constitutional amendment granting Americans the right to bear arms.

Bloomberg’s news service competes with Reuters.