A swing state in U.S. elections is a state where both major political parties (Democrats and Republicans) have similar levels of support, making it a key battleground for electoral outcomes. These states are crucial in presidential elections, as they can shift the balance of power depending on voter sentiment. Swing states often receive increased campaign attention, as candidates focus on appealing to undecided voters. Due to their unpredictable nature, they can determine the overall result of an election, influencing national policies and party strategy.