Republican Sens. Steve Daines (Mont.), James Lankford (Okla.), and Todd Young (Ind.) will join the Senate Finance Committee.

The three lawmakers, announced Jan. 3 by Senate Majority Leader Mitch McConnell (R-Ky.), will fill vacancies on the tax-writing panel resulting from Sen. Dean Heller’s (R-Nev.) loss in the November midterm elections and Chairman Orrin G. Hatch’s (R-Utah) retirement at the end of the last Congress. Republicans had a third opening to fill on the committee because Senate ratios changed...