Republicans have waged a decades-long battle to blow up the campaign-finance laws that rein in big-money spending. Now, they are making a play that could end in their biggest victory since the Citizens United ruling in 2010.

The GOP is growing increasingly optimistic about their prospects in a little-noticed lawsuit that would allow official party committees and candidates to coordinate freely by removing current spending restrictions. If successful, it would represent a seismic shift in how tens of millions of campaign dollars are spent and upend a well-established political ecosystem for TV advertising.

An eventual victory in the lawsuit, filed last November by the National Republican Senatorial Committee and the National Republican Congressional Committee, would eliminate the need for House and Senate campaign committees of any party to set up separate operations to make so-called independent expenditures to boost candidates with TV ads.