With just a week left before the Iowa caucuses, presidential candidates are getting desperate. Democrat Hillary Clinton begged her supporters Sunday to donate $1, which she said would help her match rival candidate Vermont Sen. Bernie Sanders in TV advertising in the Hawkeye State.

The message came in a fundraising email that reminded her supporters of the enthusiasm Sanders has seen in recent weeks.

“You don't need me to tell you that this race is close. My opponent is outspending us on TV advertising, getting in front of more voters at a crucial time — and he's able to do that because his supporters are stepping up across the board,” the email said. “I know what this team is capable of, and I know we can match them.”

After months of relying on mostly his grassroots support, Sanders has been outspending the Clinton campaign on broadcast advertising in Iowa since mid-November, Bloomberg reported. Clinton had a significant head start, considering her campaign began airing commercials in Iowa and New Hampshire last August. But once Sanders started buying time in the first two nominating states, he quickly surpassed her.

The Vermont senator has continued to rise in recent polls, both nationally and in the early states. Clinton maintains a double digit lead in averages of national polls, but a CBS/New York Times poll earlier this month showed her just 7 points up on Sanders, with Clinton at 48 percent and Sanders at 41 percent.

He has led her for some time in New Hampshire where he is thought to have a near-home field advantage, and in Iowa, the two candidates are neck-and-neck, with some polls showing Sanders coming out ahead of Clinton.

This is not the first time Clinton has used her fundraising emails to alert supporters to the dangers of Sanders’ candidacy. In December, a fundraising message warned she could “lose the nomination” and reminded voters the campaign would be a “hard fight.” She has also warned she could lose Iowa or New Hampshire, and a message from campaign manager Robby Mook used the subject line “nervous” to tell supporters about Sanders’ spending in early January.

For his part, Sanders’ campaign has said it has raised a significant amount of money thanks to Clinton’s criticisms, the Washington Post reported. Both candidates have stepped up their attacks over the past few weeks, and the Sanders campaign sent a fundraising email of its own accusing Clinton of making “vicious and coordinated attacks” on his healthcare plan. With the new influx of cash, Sanders strategist Tad Devine told the Washington Post his campaign may expand TV advertising beyond the three early voting states of Iowa, New Hampshire and Nevada.