Answer:
Swing states can determine the outcome in an election. A swing state can be worth a lot of points(29 electoral votes) for instance Florida is very well known to be a swing state, some times Democrats win it and most of the time Republicans win it. It can be the tie breaker, in the 2000 Election Gore(D) vs. Bush(R), Bush won by about only 537 votes out of the millions of votes casted. Intially, Gore was projected to have won the popular vote [267(Gore) to 246 (Bush) ]. But, Bush was ahead in Florida and demanded a court trial. In the court case Bush v. Gore, Bush won saying that it was unconstitutional, because in some counties, the ballots(butterfly ballots their layout is said to have been confusing.) were counted differently than other counties. And voters had a difficult time choosing the candidate.
Hope this helps!