"Based on the experience of our 2008 gubernatorial primary, there's a strong desire internally within the party to avoid having a primary fight for either race," said Parker.
In the 2008 Democratic primary, former Rep. Jill Long Thompson narrowly defeated businessman Jim Schellinger in a very competitive race. Long Thompson, sapped of money and saddled with a divided party, went on to lose by double digits to Gov. Mitch Daniels (R).
If Gregg ends up in the gubernatorial race and Donnelly enters the Senate contest, Democrats may be able to avoid the primary fight Parker cautioned against, though other lesser-known candidates remain possibilities for both races.
Donnelly's calculations will be made with an eye toward the state legislature, which controls the redistricting process in Indiana. Republicans have hoped to gerrymander Donnelly's South Bend-based seat in their favor by giving him more GOP-heavy precincts. If legislators draw a district Donnelly does not believe he can win, he would be more likely to seek a higher office.