Prayer is the western version of meditation. Do most Christians do it the way they were instructed? No. Hell no. Since that is the case, and they'd rather politicize it by doing it publicly and before hearings and other shit that some would rather not participate in, they open it to scrutiny and public pushback.
But again, prayer is "effective" in the same sense that Buddhist meditation is. When people put their minds to something, great things are made possible. Sometimes, not so great things, but when Christians do it, publicly, at least their revealing their true intentions to everyone. That's useful information to have, especially when they declare they are going to take over the government and rule like a theocracy; which nobody wants.