Indiana state Treasurer Richard Mourdock has taken a slight lead on Sen. Richard Lugar (R-Ind.) in the state’s Republican Senate primary, according to a new poll from a Mourdock-aligned group.

U.S. Senate candidates running in the GOP primary, Sen. Richard Lugar, R-Ind.,and Richard Mourdock, left, participate in a debate Wednesday, April 11, 2012, in Indianapolis. (Darron Cummings/AP)

The poll, conducted by GOP pollster Fritz Wenzel for Mourdock-supporting group Citizens United, shows Mourdock at 44 percent and Lugar at 39 percent. The poll has a margin of error of about 4 percent.

Not surprisingly, the poll shows Mourdock relying heavily on tea party conservatives, winning their vote by a margin of 63 percent to 24 percent. Those voters comprised just more than one-third of the polls respondents.

Lugar, meanwhile, leads among moderates 61 percent to 27 percent.

The poll also shows Lugar’s favorability among Republican primary voters dropping below 50 percent — to 44 percent — for the first time. His unfavorable rating has risen as well, but the polling memorandum doesn’t say precisely what it is.

The poll is part of what seems to be a steady trend in Mourdock’s favor.

A McLaughlin poll conducted last week for Mourdock’s campaign showed him up by one point. Previous polls — including another Wenzel poll for Citizen United — had showed Lugar leading by six or seven points.

But things could still change. One in four voters say they are very open to changing their minds, and only 51 percent say they are fully decided.

Lugar’s campaign said the polling doesn’t square with what they are seeing.

“All along, the Mourdock campaign has been fueled by special interests from outside the State of Indiana — and this poll is just another example,” Lugar campaign manager Emily Krueger said in a statement. “Our internal polling shows Dick Lugar is, was and will remain in the lead. Our polling also shows Richard Mourdock’s unfavorable ratings growing rapidly. The more Hoosiers learn about Mourdock, the less they trust him.

The primary is now less than two weeks away, on May 8.