New polling conducted for Democrat Elizabeth Colbert Busch's South Carolina special election campaign shows her leading both men who will face off for the GOP nomination Tuesday, including former governor Mark Sanford.

The Lake Research Partners poll shows Colbert Busch ahead of Sanford but within the margin of error, 47 percent to 44 percent. Sanford is a heavy favorite in Tuesday's Republican primary runoff.

She holds a bigger lead over the less well-known former Charleston County Councilman Curtis Bostic (R), 48 percent to 39 percent.

Internal polls and special election polls should always be taken with a grain of salt. The poll is weighted for age and race according to a turnout model determined by the pollster, and it's also worth noting that building that voter model in a low-turnout special election for a congressional seat is very difficult.

The pollster notes that Colbert Busch, the sister of comedian Stephen Colbert, has a 48 percent favorable rating, compared to a 24 percent unfavorable. It doesn't disclose personal image numbers for either Sanford or Bostic, but a South Carolina Democrat who has seen the poll says Sanford's favorable rating is 43 percent, while his unfavorable rating is 49 percent.

A poll from Democratic automated pollster Public Policy Polling last week showed a similar head-to-head number -- 47-45 Colbert Busch -- but Sanford's favorable rating was 34 percent and his unfavorable was 58 percent.

The district at stake went 58 percent for Mitt Romney in the 2012 election, but Democrats believe Colbert Busch could be competitive against Sanford, given his personal scandal that included an affair with a woman from Argentina.

That said, it would be very tough for Democrats to hold the district in November 2014, so it's not clear that it's worth the investment for national Democrats. The poll could be an effort to lure them to give her some support.