Since Donald Trump’s debate performance on Monday, he and his surrogates have teased the idea that they might attack Hillary Clinton for Bill Clinton’s past infidelities. Let’s put aside the propriety of this attack, and analyze it strictly as a political maneuver. It is dubious whether this would effectively diminish Hillary’s standing. In fact, the polling evidence points in the opposite direction, quite conclusively: focusing on Bill Clinton’s improprieties actually enhances her reputation.
Consider the following graph, courtesy of the Gallup poll, which tracks Hillary Clinton’s favorable rating since her entrance to the national stage in 1992.

As first lady, Clinton’s favorable rating was always net positive per Gallup, but typically it was relatively weak compared to other first ladies. It was only when the Monica Lewinsky scandal hit that her favorable numbers skyrocketed, in part because the public came to identify her as the victim.
Other polls from the 1990s found similar results. A Harris poll from January 1996 found 47 percent of Americans thought she was doing an “excellent” or “pretty good job” as first lady. By July 1999 that number had risen to 68 percent. Similarly, a CNN/Time poll from January 1996 gave her a 49 percent approval rating, compared to 64 percent in May 1998 from the same poll. In January 1998, just prior to the revelations of the scandal from the Drudge Report, a Fox News/Opinion Dynamics poll had Clinton’s favorable rating at 54 percent. When the House impeached him, in December of that year, it had risen to 62 percent.
Writing in Clinton, Inc., Daniel Halper points out that the Lewinsky scandal helped Hillary Clinton create a political brand independent of her husband:
How then is Trump supposed to make hay out of this? Her marital problems, if anything, have actually helped her political career. There are many lines of attack against Hillary Clinton, but history has shown that Bill’s infidelities is not one of them.