Story highlights Mitt Romney wanted a Nebraska senator to mount a third-party bid

Anti-Donald Trump Republicans are still seeking a candidate

Washington (CNN) Republican National Committee Chairman Reince Priebus says a third-party presidential campaign against Donald Trump and Hillary Clinton would be a "suicide mission."

"They can try to hijack another party and get on the ballot, but, look, it's a suicide mission for our country because what it means is that you're throwing down not just eight years of the White House but potentially 100 years on the Supreme Court and wrecking this country for many generations," Priebus said on "Fox News Sunday," anticipating that a conservative third-party candidate would split the Republican vote and ensure a Democrat wins the White House.

"So I think that's the legacy these folks will leave behind. I think it's very dangerous, and there's other ways to get assurances on the things that they're worried about," he said.

The top Republican's comments come as a group of anti-Trump conservatives seek an alternative to the two likely nominees.

Mitt Romney made an unsuccessful effort to recruit Nebraska Sen. Ben Sasse as a third-party candidate, a source with knowledge of the efforts confirmed to CNN Sunday.

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