If you're having trouble with this, I'd suggest creating a custom character, and maxing out stamina points.
After that, maybe try against lesser candidates.
If that don't work, maybe trying turning down the level you're playing.
If that still don't work, custom create an opposition party candidate. Give him minimal stats and/or have them support unpopular positions and/or oppose popular positions.
Granted, this might make the game a little too easy, if you max out your stats, play low levels, and against a customized opposition candidate with no stats, but you'll start to get a real feel for the game this way, and get you used to how the game plays, and voters respond to your actions.
Once you got it mastered that way, try ramping up the difficulty level, or ignore that customized opponent.
