Klobuchar says she's not directing supporters to do anything after Biden aides float Iowa caucus alliance

"I'm not even getting to that point yet. I want to be viable in every precinct," Klobuchar told CNN on Tuesday night in Council Bluffs, Iowa.

It's a conversation that often takes place in the closing days of the Iowa caucuses, when a voter's second choice becomes a critical piece of the political -- and mathematical -- equation. Candidates must reach a threshold of 15% support in each precinct to be viable. If they do not, supporters can resort to their Plan B.

The New York Times reported late Tuesday evening that a top Biden aide in Iowa made an overture this week to the Klobuchar campaign, hoping to win over her supporters in parts of the state where she may not be viable. Two Democratic sources confirmed the discussions to CNN.

The campaign of Pete Buttigieg, the former mayor of South Bend, Indiana, also has its eye on Klobuchar supporters. Biden, Buttigieg and Klobuchar are competing for some of the same supporters, particularly voters looking for a more pragmatic nominee.

"We are not urging them to do anything that I know of," Klobuchar said. "I'm just urging people to show up and support me."

The discussion between aides to Biden and Klobuchar involved the two moderate candidates offering guidance to their Iowa supporters to back the other in precincts where one of them does not have enough support to win delegates. The conversations underscore the urgency Biden is facing as he is locked in a tight battle with Vermont Sen. Bernie Sanders, who is closing the Iowa caucus campaign with a late surge.

While a caucusgoer's second choice becomes crucial in the Iowa contests, voters say in interviews they are more likely to follow their own instincts rather than follow the lead of a campaign.

A candidate needs 15% of the vote to remain viable in the caucus at their precinct location, as determined by the amount of people participating in that location. If a candidate isn't viable, their voters can realign to another viable candidate or band together to form a group in support of another candidate that meets the threshold.

A senior Klobuchar aide confirmed to CNN that the offer happened over dinner and drinks at a Des Moines, Iowa, restaurant between old colleagues who have known each other for some time.

"This was not a serious conversation and was dismissed," the Klobuchar aide said.

The conversation was between Jake Braun, Biden's state director in Iowa, and Pete Giangreco, a longtime Klobuchar adviser. Braun and Giangreco worked on Obama's 2008 presidential campaign together.

The Biden campaign did not comment on the conversations about the alliance.

Klobuchar's slow rise in Iowa could complicate the Biden and Buttigieg efforts, with three candidates dividing support in the so-called moderate lane, while Sanders and Massachusetts Sen. Elizabeth Warren are occupying more of a progressive lane.