if a party get's a high enough percentage of the vote to govern alone, then fair enough.
If they don't, then they shouldn't be able to govern alone, and should have to compromise to reach agreement with other parties either in coalition, or via a minority government on an issue by issue basis.
it works fine in a lot of the worlds most successful countries, and in theory ought to help prevent the worst excesses of wannabe presidents forcing through extreme policies because they have enough of a majority to even ignore their own parties rebels.
without this, you've essentially got the biggest minority opinion able to dictate to everyone else for 5 years, which is a pretty odd version of democracy IMO.