WATCH LIVE: President Trump speaks at H&K equipment company in Pennsylvania
President Donald Trump campaigns for Roy Moore in Pensacola, FL (Screen capture)

After a critical loss for Republicans in Alabama last month, President Donald Trump is wading back into congressional politics on Thursday when he travels to western Pennsylvania to signal his backing for the party's candidate in a special election.

Trump is scheduled to give remarks at H&K at 3:05 p.m. (ET). Watch live video below:

Trump said on Twitter on Thursday he was making the trip "in order to give my total support" to Rick Saccone, the Republican seeking to replace Representative Tim Murphy. Murphy resigned in October amid a sex scandal.

"Rick is a great guy. We need more Republicans to continue our already successful agenda!" Trump said.

Saccone will meet Trump on the tarmac when he lands in Pennsylvania. Afterward, Trump will tour an industrial equipment company outside Pittsburgh, where he will tout the tax-reform legislation passed by Congress last month.

The Democratic candidate in the March 13 election to replace Murphy is Conor Lamb, a former Marine and U.S. attorney.

The race is being watched nationally as an indicator of whether Democrats can be competitive in Republican-leaning congressional districts ahead of November's mid-term elections, when control of both houses of Congress will be at stake.

Trump won the district by nearly 20 points in the 2016 presidential election and surprised political observers by winning Pennsylvania, traditionally a Democratic-leaning state, by less than 1 percent.

In an interview with Reuters on Wednesday, Trump pledged to be heavily involved in congressional races, including the one to replace Murphy.

Trump’s last foray into congressional politics did not go well.

In a special U.S. Senate election in Alabama late last year, the president first backed the incumbent candidate in the Republican primary, Luther Strange, who had been named temporarily to fill the seat vacated by Jeff Sessions when Trump named him U.S. attorney general.

After Strange lost to Roy Moore in the primary Trump switched his support to Moore. The president stood by him even after Moore was accused of sexual misconduct - allegations that the Republican candidate denied.

Moore lost to Democrat Doug Jones in the general election, a stunning result in deeply conservative Alabama and shaving Republicans' majority in the Senate to 51-49. Exit polls showed many voters turned out to register their disapproval of Trump.

On Tuesday, Democrats scored an upset in a Wisconsin state Senate special election in a district Trump won by about 17 points.

Republican Wisconsin Governor Scott Walker on Twitter called the result “a wake up call” for the party there.

(Reporting by James Oliphant; Additional reporting by Ayesha Rascoe; Editing by Caren Bohan and Jeffrey Benkoe)