ST. PAUL — Amid mounting public legal costs, Minnesota senators vowed Thursday to keep fighting a lawsuit filed by a veteran aide that was fired for an affair with the Republican majority leader.

Senior senators approved payment of the latest $90,000 invoice from a private firm defending the chamber against claims by Michael Brodkorb. One Democrat on the Rules and Adminstration Committee voiced concern over $200,000 of legal bills in all, but Republicans said it would be a mistake to give in to what they consider meritless claims just to make the case go away.

“A decision like this is precedent-setting and if we don’t stand on our heels and put despite some cement around them on this, we’re going to set a precedent that is going to be with the Senate for decades to come,” said Senate Majority Leader David Senjem, who took over after his predecessor gave up his post in the scandal. “I think we believe we are right. We ought to stand on what we believe is right. In my view, that’s why we have courts.” Senjem said settling would be perceived “as a cover-up, which we don’t want.”

Brodkorb was a $90,000-a-year communications aide to Senate Republicans. He was fired last year when his affair with then-Senate Majority Leader Amy Koch became public.