As the US presidential campaign heats up, candidates are ramping up advertising efforts to get in front of potential voters. Bernie Sanders, in particular, is edging ahead of his Democratic rival Hillary Clinton.

In the last two months, the Vermont senator’s campaign spent nearly $8 million on advertising, according to data from ad-tracking firm SMG Delta, as cited by NBC News. That brings his total to $12.8 million spent on advertising through Jan. 19, ahead of the $11.6 spent by Clinton and her super PACs.

The hike puts Sanders ahead of Clinton in terms of ad spending for the first time in the election cycle.

Right now, Sanders’ investment seems to be paying off. His ads are hit with Democrats and Independents, he has pulled within 5 points of Clinton in Iowa, and he leads her by double digits in New Hampshire. Nationally, however, Clinton has a commanding advantage.

The leading Democratic candidates each released new TV ads this week, ahead of the Iowa caucus. The Sanders ad, featuring the Simon & Garfunkel song “America,” offered a message of hope to voters, while Clinton’s positioned her as the only hope for defeating the Republicans.

On the other side of the aisle, Jeb Bush and Marco Rubio continue to vastly outspend their rivals. Bush and Rubio, along with their super PACs and outside groups, spent a combined $91 million on advertising, the SMG Delta data shows. Meanwhile, Republican frontrunners Trump and Cruz, including Cruz’s outside groups, spent a paltry $8.2 million.

Trump and Sanders may not agree on much, but they are the only candidates in the 2016 presidential race to pay for ads entirely with their own campaign dollars. Both candidates have spoken out against big money in politics in recent weeks.