MUSCATINE, Iowa — Inside a home packed to the gills in Muscatine, Iowa, Beto O'Rourke introduced himself as a presidential candidate.      

"It's my honor to be here with you, to have the chance to introduce myself and most importantly to listen to you," he told supporters who stuffed into the house.

The so-called "house party" capped off a whirlwind day in Iowa for the former congressman from Texas. Early Thursday morning, he officially announced his candidacy on social media. He joins an already crowded Democratic field, including senators Kamala Harris and Cory Booker, as well as fellow Texan Julian Castro.

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"It’s a great sign in some important ways this democracy still works," O'Rourke said of the many candidates.

Hours after he announced, he started his Iowa tour. He stopped at a high school, a sandwich shop and a cafe, among others, where he hopped onto the counter to speak to and listen to potential voters.

"Los imigrantes tambien," he told a reporter in Spanish, meaning "immigrants too."

He focused on health care and education and spotlighted his concerns on climate change.

"The scientists are absolutely unanimous on this, that we have no more than 12 years to take incredibly bold action on this crisis," he said at a cafe.

And in Iowa, the focus was on the future.

"That’s our moment right now, a defining moment of truth," he said. "And we are going to meet it together. Are you with me on this one?"

A much-speculated-about candidacy that is, indeed, happening.

O'Rourke will spend the next two days in Iowa before traveling around the country. He'll then launch a campaign kick-off event on March 30 in El Paso.