Story highlights Mitt Romney was the 2012 Republican presidential nominee

He made a donor call for Marco Rubio

(CNN) Former Republican presidential nominee Mitt Romney is helping Florida Sen. Marco Rubio's re-election campaign through private donor outreach, CNN has learned, an effort that comes as the party's down-ballot candidates struggle to navigate a political climate dominated by Donald Trump.

On a call to about 20 potential Rubio donors on Wednesday, Romney said that given the likelihood of victory for Hillary Clinton in November, it was important to devote financial resources toward holding seats like Rubio's to serve as a check to a Democratic president, according to a recording of the conversation obtained by CNN.

"The unfortunate truth about this election is that nobody's really happy -- I shouldn't say nobody -- most Americans are not really happy with either outcome, either the Republican or Democrat outcome. But right now, Hillary's in the lead," Romney said.

He added: "And if she were to win by too large a margin it would be very, very hard for us to be able to maintain the principles to keep America the nation that it is. It's important that regardless of what happens on the presidential level, that we have Sen. Rubio able to be successful and win in Florida so we can maintain our majority in the Senate."

As a presidential candidate earlier this year, Rubio initially said he wouldn't run for re-election to the Senate, but he changed his mind after dropping out of the White House race in June.

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