Massachusetts Senator Elizabeth Warren was in Iowa last weekend. That's after announcing she's formed an exploratory committee to run for president.
As someone who's testing the waters on running for president but hasn't officially announced, there's a lot Warren can't do under federal law.
She can't call herself a candidate, or hand out any "Warren 2020" buttons.
But there are advantages to forming an exploratory committee.
For one, Warren can raise money without disclosing the donors or amounts until she decides to run.
Sheila Krumholz, the executive director of the Center for Responsive Politics — a campaign finance watchdog group — said the secrecy can offer candidates a way to narrow the field of candidates.
"It's nice to be able to announce a big kind of money bomb to really make your competition shake in their boots," she said. "So they want to be able to come out with a bang, once they do actually declare their official candidacy."
Krumholz said an exploratory committee also gives a candidate the opportunity to drum up more excitement by essentially launching their campaign twice.