The case for a debate
Václav Klaus has maintained his 60%+ approval rating by counterbalancing his oft-perceived negative traits (divisiveness, pedantry) with his generally accepted positive traits (erudition, hard work, conviction of opinion). The risk presented by Jan Švejnar isn't that he can defeat Klaus, but rather that he'll be used by the anti-Klaus coalition to shift the fine balance of public opinion out of Klaus's favor by dwelling on Klaus's negatives. By making the political decision to topple a bruised Klaus more palatable to the public, Klaus's detractors could open the way for a new, as-yet-unknown candidate to emerge if no one wins in the early balloting. Although it seems counterintuitive now, Klaus might decide that the best way to confront this risk is by meeting it head-on and agreeing to a debate with Švejnar. A strong debate by Klaus now could help prevent the emergence of a sleeper candidate later.