As was hinted above, if they counted only the popular vote then strategies would change, and we don't really know how things would turn out.

In a practical sense, eliminating the College would make presidential elections fabulously expensive, even by current standards, because the state boundaries do let the candidates identify safe, swing, and lost areas and decide where to allocate money.

As mentioned above, the College makes fraud less beneficial, because its effect is restricted to one state. In 1860, Lincoln drew only about 25,000 votes in slave-holding states, with about two-thirds of those around St. Louis. That wasn't because no one there wanted to vote for him - it was because he was left off ballots and votes that were cast weren't counted. He was credited with less than 5% of the votes in those states, but the damage was limited to those states and Lincoln took the election winning all of the states that honest elections.

People assert that Lincoln's election was a fluke because there were four candidates in the field, but he took more than 50% of the vote in states with 167 electoral votes, out of a total of 303 available.