Hillary Rodham Clinton spent $26 million over the summer building up her 2016 campaign, more than any of her rivals either within her own Democratic Party or the Republican side, as she sought to build a formidable organization to help her capture the White House.

The former first lady and secretary of state who lost to Barack Obama in the 2008 campaign poured money into television advertising, the amassing of polling data and building a digital operation to reach as many voters as possible. Her biggest expense was the payroll for the 511 people her campaign employs, figures released Thursday show.

Clinton is attempting to strike a delicate balance. She's willing to spend the money to build an operation that no one else vying for the White House can compete with. At the same time, she wants to keep spending in check so that the campaign's budget doesn't spiral out of control.