Milwaukee and Madison were among dozens of Wisconsin cities that joined the second wave of "No Kings" demonstrations nationwide on Oct. 18 in what organizers are calling the largest single day of protest in modern American history.

For the second time this year, southeast Wisconsin joined nationwide "No Kings" protests on Oct. 18. They've served as a way for protesters to call out what they deem an abuse of power by President Donald Trump and his administration.

Many held signs making fun of the president; some wore costumes — a frog suit, an inflatable Cookie Monster — joining a trend that began during protests of immigration raids in Portland, Oregon. There were many American flags,

MADISON, Wis. -- Madison police said an estimated 15,000 people attended Saturday's "No Kings" protest downtown. The group gathered at McPike Park at around 2 p.m. then marched up East Washington Ave. to the Wisconsin State Capitol.

Organizers say the energy Saturday will be a message to both Trump and elected Democratic leaders that people want change.

This is the third mass mobilization since Trump's return to the White House and it is expected to be the largest.