Sen. Blanche Lincoln (D-Ark.) raised about $1.3 million from January to March, her campaign announced Tuesday.

However, her primary opponent, Lt. Gov. Bill Halter (D), surpassed that six-figure haul by raising $2 million in his first four weeks as a candidate, according to the Associated Press.

Lincoln still has the cash-on-hand edge, as she ended March with more than $4.3 million in the bank.

Leading progressive groups such as MoveOn.org lobbied for Halter’s candidacy. Several of those groups have pledged to spend millions to try to defeat Lincoln, whom they view as too moderate, in the May 18 primary.

Lincoln is also a top target for the GOP this cycle, and more than half a dozen Republicans are vying for their party’s Senate nomination.

The leading GOP candidates include Rep. John Boozman, state Sen. Gilbert Baker, state Sen. Kim Hendren and former state Sen. Jim Holt.