Republican House member from Louisiana Vance McAllister is under pressure from fellow Republicans to resign after information came to light about an affair between the (married) congressman and a (married) member of his staff. That would be a huge mistake.
Louisiana is also the state whose incumbent Republican senator was revealed to be a regular customer of a prostitute, so it's a little difficult to detect a principled issue here. The differences are all political, and they absolutely indicate that Republicans are smart to try to nudge McAllister aside. But they also indicate that McAllister should refuse.
The thing about McAllister is that he's a freshman in what should be a safe Republican seat. Having him enmeshed in scandal potentially puts the seat at risk, and as a freshman he has no longstanding ties to the caucus or inside connections. The good outcome for the GOP is for him to quit, and be replaced on the ballot with Generic Louisiana Republican X who will win easily. But the flipside is that if McAllister can credibly demonstrate that he's not quitting, the GOP leadership has to rally around him. This is a very Republican seat — Mitt Romney got 61 percent of the vote in 2012 — so it's winnable even with a scandal-plagued candidate as long as everyone on Team GOP agrees to support the Republican.
And in this era of polarized politics, why shouldn't they? McAllister will be every bit as much a reliable vote for Paul Ryan's budget ideas as any other Republican would be.