Republicans are worried that Donald Trump's presidential candidacy may hurt down-ballot races and cost the GOP its Senate majority, Democrat Bill Richardson told CNBC on Friday.
"There's serious concern among Republicans, and I have a lot of Republican friends, ... about losing the Senate," Richardson said in a "Squawk Box" interview. "The House is probably going to be OK [for the GOP], lose some seats. But the Senate is in play."
Richardson, who unsuccessfully sought the Democratic presidential nomination in 2008 and supports Hillary Clinton, was energy secretary during Bill Clinton's presidency. Richardson was also governor of New Mexico and U.S. ambassador to the United Nations.
Recent polls nationally and in battleground states have been favoring Clinton. "I've been in elections," said Richardson. "Polls do matter."
But Betsy McCaughey, former Republican lieutenant governor of New York, dismissed the polls, telling CNBC in the same interview it's a long way to the November election.
"Eighty days, three presidential debates to go. In politics that is an eternity," said McCaughey, who's a columnist for the New York Post. "Voters really have a choice: class warfare or growth."
McCaughey said Trump's economic plan, including a reduction of corporate taxes, would promote growth.
"You can't clobber corporations with the highest tax rates in the world, and then say you want to boost manufacturing," McCaughey said, referring to Clinton's "Make it in America" push and claims companies pay too little in taxes.
Richardson defended Clinton: "I think the 1 percent and the corporations, they deserve their fair share of taxing."
Meanwhile, the Trump campaign on Friday released its first television general election television ad, saying the system under Clinton "stays rigged" against Americans.
At the same time, Trump struck a softer tone on the campaign trail, saying at a North Carolina rally he regrets comments that "may have caused personal pain." It was the GOP nominee's first speech since a shake-up in his campaign staff this week.
While calling the so-called New Trump "terrific" and praising new campaign manager Kellyanne Conway, McCaughey said: "This is not about personality."
"This election will turn on the economy," she added.
Richardson said he was not surprised that Trump toned down his act. "Obviously he has to change his tone because he's had a disastrous month since the convention."
McCaughey countered by saying: "What happens in August stays in August."