FORTUNE -- In the fall of 1996, I sat inside weekly strategy meetings of conservative activists, as part of research for my book, Gang of Five, chronicling the rise of the baby-boomer right. The war-room host was famed anti-tax activist Grover Norquist and with Bill Clinton on the verge of re-election, the question on the table was this: How to convince lawmakers to open impeachment proceedings against the President?
Mind you, this was a full year before any one had ever heard the name Monica Lewinsky. But the activists -- briefed by Republican staff investigators on Capitol Hill -- were certain they could find something, anything, in Kenneth Starr's Whitewater investigation to justify booting him from office. The atmosphere was so thick with thirst for political blood that one activist, a lawyer, finally felt compelled to cut in: "I don't think we ought to go around impeaching presidents lightly."
With strong Republican gains on the horizon Tuesday, the GOP should remember a key lesson from the Clinton years: The politics of destruction, while tempting, usually backfires. After Tuesday, GOP leaders will face two choices: Do they seek out opportunities to work with President Obama if (and this remains a big "if" based on the record) he's willing? Or should their modus operandi be to crush him in advance of the 2012 presidential election?
Flash back to the 1990s. The activists in that room finally got their wish when Lewinsky surfaced as Clinton's intern-lover and he lied about it. Impeachment proceeded, Clinton's enemies gloated, and guess what happened? Republican popularity tanked, and the party lost House seats in the 1998 midterms.
Likewise, three years earlier, a budget confrontation between congressional Republicans and President Clinton led to twin government shutdowns. Clinton's popularity soared -- just a year after his party's brutal shellacking in the midterms.
Opposing the current Obama agenda to date is fair game. Most voters don't think the stimulus worked, and they side with Republicans in supporting repeal of at least some portions of healthcare reform that Democrats squeezed through on a mostly party-line vote. But demonizing the President -- or refusing to work with him on any of a host of fiscal issues bedeviling the nation as we move forward -- is a dangerous miscalculation of the public mood.
Just look at the recent ABC News/Washington Post Poll: 67% of voters disapprove of the way Republicans in Congress are doing their job. Only 30% approve, a result echoed in range of polling. That's not exactly a back slap.
Republican leaders who return to Capitol Hill in January with enhanced ranks need to remember that this is a backlash election, not a mandate election. Step gingerly.
Last week Senate Republican Leader Mitch McConnell drew fire from the White House and allies in the media for telling National Journal's Major Garrett that "the single most important thing" he wants to achieve is a Republican victory in 2012. "The Republican leader of the Senate said his main goal after this election is simply to win the next one," President Obama complained in his Saturday radio address.
In fact, if you read the full interview, McConnell made clear his "political" priority was to "give our nominee the maximum opportunity to be successful." Mostly, he dwelled on how the problem of tea-party-backed confrontationists and how to both manage their expectations and move forward on policy with more of them in his ranks.
"We do not control the government and cannot control the government when the president holds the veto pen," McConnell said. "We need to have a humble, grateful response about this election. Incidentally, there is no polling data that suggests [the voters] love us."
If GOP leaders keep that in mind, they might be able to move toward 2012 on Barack Obama's campaign pledge -- arguably his greatest shortcoming as president so far -- to pursue "unity of purpose over conflict and discord."