Former New Mexico Republican Party Chairman Allen Weh will officially launch a bid against Sen. Tom UdallThomas (Tom) Stewart UdallOvernight Energy: Spending bill targets Pruitt | Ryan not paying 'close attention' to Pruitt controversies | Yellowstone park chief learned of dismissal through press release Senate committee targets Pruitt scandals in spending bill Overnight Energy: DNC to reject fossil fuel donations | Regulators see no security risk in coal plant closures | Senate committee rejects Trump EPA, Interior budgets MORE (D-N.M.) on Thursday, according to the Santa Fe New Mexican.

Weh, a businessman who finished second in a five-way gubernatorial primary behind New Mexico Gov. Susana Martinez (R) in 2010, will announce his candidacy via Web video. He's long been expected to run for the seat.

Udall is viewed as safe in the Democratic-leaning state. But Weh has the ability to self-fund much of his campaign — he spent $1.6 million of his own money in his race against Martinez — and could force Udall to spend more money than he otherwise would have had to.

Libertarian-leaning Republican attorney David Clements is also in the race.