Larry Hogan, the ex-GOP governor of the largely Democratic Maryland, has declared his Senate candidacy, vowing to “challenge both parties” if he wins.

“I am running for the United States Senate – not to be loyal to one party – but to confront both parties, defend Maryland, and repair our nation’s dysfunctional politics,” Mr Hogan posted on X as he announced his run.

That’s how I governed Maryland, and that’s how I’ll represent Maryland in the Senate. Let’s get to work.”

The well-liked ex-governor posted a video, where he declared: “We urgently need leaders who can challenge both parties — leaders who understand that none of us have all the solutions or all the authority, because this is not only about the divide between the right and the left.

“This is about the distinction between right and wrong.

Mr Hogan will file the official papers before the state’s deadline on Friday.

The ex-two-term state leader’s new run could boost the Republicans’ already high odds to reclaim the US Senate from Democrats.

The Cook Political Report has called Mr Cardin’s seat a “solid Democrat” but Mr Hogan’s run could change the game given his strong popularity in the state.

Now, Mr Hogan is a clear frontrunner to get the Republican senate ticket, and he may face either US Representative David Trone or Prince George’s County Executive Angela Alsobrooks on the Democratic side.

Mr Hogan’s decision follows strong urging by the National Republican Senatorial Committee and its chair Montana Senator Steve Daines, The Hill reported.

The 67-year-old also talked to South Dakota Senator John Thune about a potential run.

Mr Hogan left the Maryland governor’s office last year with a 77 per cent approval rating after two terms, starting in 2015. He’s aiming to replace the retiring Democratic Maryland Senator Ben Cardin, 80.

Last year, Mr Hogan dismissed the idea of running for the senate in a NewsNation interview, and also hinted at a third-party presidential run.

The last time Maryland voted for a Republican in a presidential race was in 1988 when it backed then-Vice President George HW Bush over Massachusetts Governor Michael Dukakis.