Elizabeth Warren teases 2020 announcement on February 9

"One month ago today, we launched this exploratory committee to build a grassroots movement to level the playing field," Warren tweeted. "On Sat, February 9, I'll be making a BIG announcement about my 2020 plans."

Warren was the first major Democratic candidate to announce an exploratory run, on New Year's Eve. Since then, the senator has traveled to the early primary states of Iowa, New Hampshire and South Carolina, and last week visited Puerto Rico, using the trip to slam President Donald Trump's handling of Hurricane Maria recovery efforts as well as his insistence on building a wall along the US southern border.

According to a Warren aide, the senator is expected to hit the trail again soon, launching a multi-state swing on the same day as her aforementioned announcement.

Warren's expected announcement next weekend comes as several of her colleagues in the Senate are still mulling White House bids of their own, including Sens. Cory Booker of New Jersey and Bernie Sanders of Vermont. Other candidates being closely watched include former Rep. Beto O'Rourke of Texas and former Vice President Joe Biden.

As the Democratic field begins to take shape in the coming months, the candidates will be questioned and scrutinized on their platforms and policy positions. Last week, Warren unveiled a "wealth tax" proposal that would levy a 2% tax on American households with wealth above $50 million, and a 3% tax on billionaires.

Health care is already a major focus in the Democratic primary. Sen. Kamala Harris of California, who launched her presidential campaign last weekend, made waves at a CNN town hall on Monday in Iowa when she said about private insurance: "Let's eliminate all of that."