Musharraf cannot afford less than a landslide for his party; otherwise he risks facing an opposition in parliament that could invalidate his extra-constitutional declaration of emergency rule. At the very least a two-thirds majority could unseat him. A two-thirds majority in parliament could also call for the reinstatement of the original Supreme Court, which Sharif says is his party's primary goal. That reconstituted high court could then rule that Musharraf contravened the constitution by dismissing the judges in the first place and declaring emergency. And, what is most worrisome for Musharraf, working outside the constitution in Pakistani law can be considered treason.
You can read more about my thoughts on "Busharraf" and his Abraham Lincoln speech at This American Muslim.