WASHINGTON - Wisconsin Governor Scott Walker will announce later Monday that he is dropping out of the GOP race for the White House, sources tell CNN.

CNN reported Monday that a GOP strategist close to the campaign and a senior GOP adviser with knowledge of Walker's plans said the governor will make the announcement at a 6 p.m. ET news conference in Madison, Wisconsin.

Walker received strong early support in Iowa and touted his record battling unions back in his home state, but fell behind in the polls after lackluster debate performances. The latest CNN / ORC International poll showed Walker received less than one-half a percentage point of support from conservatives.

The same poll showed Donald Trump leading the crowded GOP field of candidates at 24 percent, with fellow business executive Carly Fiorina surging behind at 15 percent after a second favorable debate performance.

Governor Bobby Jindal polled in the same position as Walker, receiving less than a percentage point and falling behind "No one / None" in the poll. Jindal qualified last week to appear on the South Carolina primary ballot, an indicator he does not intend to exit the race.

The poll included answers from registered voters who identified as Republican or Republican-leaning, with a sampling error of +/-4.5 percent.