The news that billionaire Michael Bloomberg might mount a third-party bid for the White House has sent ripples through the political world, but analysts and activists differ on whether he is just sending a message or really is serious about a campaign.

Bloomberg, the former New York City mayor, is taking steps for a run, according to stories Sunday quoting unnamed sources, because he’s galled by the dominance of Donald Trump among Republicans and the rise of Sen. Bernie Sanders (I-Vt.) on the Democratic side.

Bloomberg is reported to be weighing personally spending $1 billion on a campaign, a daunting prospect for possible opponents.

Bloomberg has not talked publicly about a bid since the stories ran. His spokesman Stu Loeser declined to comment.

But the stories have spurred speculation about his plans and motivations.

The camp that thinks Bloomberg is mainly sending a message cite the timing and method of making his interest known — a leaked story a week before the Iowa caucuses — and the fact that no third-party candidate has won the presidency.

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The story hit as Sanders surged in New Hampshire and Iowa polls, suggesting “this is a ‘stop Sanders’ effort,” said Neil Sroka, spokesman for the progressive nonprofit Democracy for America, which is backing Sanders.

“Bloomberg is extremely close to Wall Street,” Sroka said, and Sanders campaigns against it. Bloomberg also has ties to Democratic candidate Hillary Clinton, who the former mayor would not likely challenge, Sroka said.

Ari Fleischer, former spokesman of President George W. Bush, said Bloomberg’s exploration of a run “is aimed squarely at Sanders if he wins, and it’s putting a toe across the line in case Hillary gets indicted,” a reference to the federal inquiries into Clinton’s use of private email as U.S. Secretary of State.

Those who say Bloomberg is really interested in running noted that he has flirted with the idea before, but the race has never been up for grabs as it is this year.

“He turns 74 next month, so he may figure that 2016 could be his last shot,” said John J. Pitney Jr., a politics professor at Claremont McKenna College, in Claremont, California. “If voters see their major-party choices coming down to a communist and a crackpot, then he will get in.”

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Trump said he’d like to compete against Bloomberg but doubts he will run. Clinton said she’ll win the Democratic nomination so he won’t have to run.

If Bloomberg does get in the race, he likely would lose but would also siphon off votes, mostly from the Democrat because of his socially liberal views especially on gun restrictions, Pitney said.

Robert Zimmerman of Great Neck, a Democratic National Committeeman and Clinton friend, said he isn’t worried about speculation about a Bloomberg campaign.

“To put this in perspective, this is fantasy baseball for political pundits,” Zimmerman said.