Washington (CNN) South Carolina Democrat Jaime Harrison announced on Wednesday he will seek to unseat GOP Sen. Lindsey Graham, who is up for reelection next year.

The bid is an uphill climb for Harrison against Graham, who has become one of President Donald Trump's most prominent supporters in Washington after being a fierce critic on the 2016 campaign trail, both before and after his own presidential run. Harrison -- a top Democratic Party official, previous state party chairman and former lobbyist -- is making his first run for public office, according to his campaign.

According to state records, Trump carried South Carolina in 2016 with 55% of the vote, compared with Democratic nominee Hillary Clinton's 41%, and Graham last won reelection in 2014 by just over 54% to his Democratic opponent's share of nearly 39%.

Harrison announced his bid in a video message posted on Wednesday, where he talked about his own background in the state and nodded to health care, student loans and Graham's long record in politics -- particularly the senator's change of opinion on Trump.

"Here's a guy who will say anything to stay in office," Harrison said of Graham. "Lindsey Graham can't lead us in any direction because he traded his moral compass for petty political gain."