The website asks supporters to provide their name, e-mail address, zip code, and an optional message of support for the police, firefighters, and EMTs who responded to the bombing. According to an FBI affidavit released Monday, three people were killed and more than 200 more were wounded in the terrorist attack.

A spokesman for the DNC accused Priebus of "politicizing" the gesture of support.

"Our supporters were looking for an outlet to express their gratitude and support for first responders in the wake of the tragedy in Boston, and collecting messages of thanks to deliver to them we concluded was the best outlet we could give them," DNC spokesman Brad Woodhouse said. "What’s disgraceful is that Republicans would stoop so low as to politicize the simple act of thanking the brave men and women who put their lives on the line to keep us safe."RNC spokesman Sean Spicer subsequently asked if DNC officials would pledge not to use information gathered for fundraising. Woodhouse responded by hitting Republicans over the sequester, $85 billion in across-the-board cuts implemented when lawmakers failed to strike a budget deal earlier this year.

This post was updated at 5:44 p.m.