What year was the Super PACs first became an important factor in national elections in?

Super PACs first became an important factor in national elections following the 2010 Supreme Court decision in Citizens United v. Federal Election Commission. This ruling allowed for the creation of independent expenditure-only committees, which could raise and spend unlimited amounts of money to influence elections. Their impact was notably seen in the 2012 presidential election, where they played a significant role in funding campaigns and political advertisements.