Cal Cunningham speaks to supporters after losing in a primary runoff for a U.S. Senate seat in 2010. (Chuck Burton/AP)

Cal Cunningham, a former North Carolina state senator courted by national Democrats to take on Sen. Thom Tillis (R-N.C.) next year, formally announced his candidacy Monday, setting up what could be another hard-fought contest in the swing state.

In a video, Cunningham, who had launched a campaign for North Carolina lieutenant governor next year, said he was instead seeking to come to Washington “to take on the political corruption that’s standing in the way of progress.”

Cunningham, an Iraq and Afghanistan wars veteran who is well-known in North Carolina political circles, drew immediate criticism from the Tillis campaign, who seized on his change in contests and accused him of being controlled by Democrats in Washington.

“Out of touch liberal Cal Cunningham enters this race by abandoning his previous commitment and demonstrating his total inability to say ‘no’ to Chuck Schumer,” Tillis campaign manager Luke Blanchat said in a statement, referring to the U.S. Senate minority leader. “It took awhile, but Schumer and the liberal Washington elite finally found someone more loyal to them than to the voters of North Carolina.”

In 2014, Tillis, a former speaker of the state House of Representatives, defeated first-term Democratic incumbent Kay Hagan by 1.5 percentage points in a contest on which both national parties spent heavily.

During that year’s primary, Tillis bested several tea party challengers to win the nomination, in what was viewed as a major victory for the GOP’s establishment wing.

Next year, Tillis is facing multiple challengers in the primary, including Garland S. Tucker III, chief executive of a Raleigh investment company. Since President Trump took office, Tillis has drawn scorn from some of the president’s supporters for opposing parts of his agenda.

Besides Cunningham, two other Democrats — Mecklenburg County Commissioner Trevor Fuller and state Sen. Erica Smith — have also announced campaigns for Tillis’s seat, but neither has gained much traction.

Cunningham has run for the U.S. Senate before. In 2010, he lost a primary runoff to Elaine Marshall, who was defeated in the general election by Sen. Richard Burr (R-N.C.).

“North Carolinians are hard-working common-sense, decent and stubbornly independent people,” Cunningham said in his new announcement video. “And you deserve to be represented by somebody who gets it.”

Felicia Sonmez contributed to this report.