CNN:

Democrat Tom Vilsack is abandoning his bid for the presidency after struggling against better-known, better-financed rivals, a senior campaign official told The Associated Press on Friday.

Vilsack left office in January and traveled through states holding early tests of strength. He had faced a tough challenge from rivals such as New York Sen. Hillary Rodham Clinton, Illinois Sen. Barack Obama and John Edwards, who have had more success raising money and attracting attention — even in Vilsack’s home state of Iowa.

Vilsack was scheduled to make a formal announcement later in the day. The official spoke to the AP on condition of anonymity to avoid pre-empting the Democrat’s statement.

Via Patrick Ruffini, who writes:

It’s easy to ascribe this to the oxygen being sucked up by HillaryObamaEdwards. The incredibly early start to the campaign is a double-edged sword for the back of the pack. Their ability to raise fast money online if they catch on late in the season is a potentially game-changing opportunity. At the same time, conventional wisdom about who’s up and down is congealing earlier, creating potential cash-flow problems for a candidate like Vilsack, who had already hired 50 staffers in Iowa.