JEFFERSON CITY, Mo. - UPDATE: 10:30 a.m.: The Missouri Democratic Party released this statement in response to Hawley's announcement:
"Two months ago, Josh Hawley filed paperwork to run for United States Senate -- and then lied to Missourians about it while he raised money behind closed doors with millionaires, DC special interests, and Republican leaders in Washington. It's clear who Josh Hawley is running to represent in the United States Senate, and it's not Missouri."
UPDATE: 5:15 a.m: Missouri Attorney General Josh Hawley's campaign has released its first video ad for his run at United States Senate.
In the ad, Hawley takes direct aim at Democratic incumbent Claire McCaskill, accusing her of being out of touch with Missouri values and turning her back on farmers and working families.
Hawley also says running for the Senate seat wasn't something he planned on doing, possibly acknowledging Hawley's accusation of Jefferson City politicians "climbing the ladder, using one office to get to another." In the ad, Hawley said it's something he has to do "to win a better future for our country."
In August, Hawley created an exploratory committee, allowing him to begin fundraising for the campaign without officially announcing his candidacy. Throughout summer, Hawley has been reportedly speaking with national party officials and appears to have the backing of Steve Bannon - former Trump advisor and executive chairman of conservative news site, Breitbart.com.
According to the Federal Election Commission, there are four other Republican candidates registered for the 2018 Senate race.
This race will likely gain national attention since McCaskill is one of 10 Democratic Senators running for re-election in states won by President Trump. If those states change to Republican, it would widen the Republican majority that currently sits at 52 to 48.
ORIGINAL STORY: Missouri's Attorney General will formally announce a campaign to run for the U.S. Senate in 2018, according to the Associated Press.
Hawley, who was elected to his current position in 2016, will be vying for the chance to take on Sen. Claire McCaskill, who will seek her third term in Congress. Hawley is expected to release a video Tuesday morning formally announcing his candidacy.
This is a developing story. Stay with ABC 17 News for more updates as they become available.