Oregon Sen. Jeff Merkley said Wednesday that the high cost of campaigning for president is one of the big factors that could keep him out of the Democratic primary field in 2020.

Merkley last year made several visits to early primary states and indicated at one point that he would decide before 2018 ended. But in his first public appearance after the holidays, Merkley said he is now looking toward the end of March for a decision.

In an interview with OPB before holding a town hall in east Portland, Merkley said he’s still weighing several concerns. Perhaps chief among them is the high cost of mounting a presidential challenge — something he said could cost tens of millions of dollars.

“You would really have to build a vast operation to be competitive given the design of our primary system,” Merkley said, “and that would require an all-out effort. And so it’s balancing that effort against putting all my efforts in through the Senate.”

He noted that at least three of his potential rivals are billionaires and that several others have built national followings allowing them to raise large sums of money on the internet.

Contenders have to build large staffs to compete at the grassroots level in Iowa and New Hampshire. And California has moved its primary to March 3, requiring candidates to mount expensive advertising and get-out-the-vote efforts in the nation’s largest state early in the primary season.

Also complicating Merkley’s decision is the fact he is up for re-election in 2020. He could test his appeal in a presidential race in the early primaries and still file for re-election by March 10.

But spending so much time out of state on the campaign trail could affect his political standing in Oregon.

Merkley said that if he does run for president, he will emphasize three big themes. They include working to combat what he calls “climate chaos,” fighting the influence of big money and voter suppression efforts in campaigns, and ending the “neglect of the foundations for thriving families.”