The 2010 Republican primary for Senate in Missouri seems to be heating up, the St. Louis Post-Dispatch reports, with frontrunner Rep. Roy Blunt and a possible opponent already going at it -- even though the opponent hasn't officially gotten in yet.

Late last week, Blunt's campaign attacked Thomas Schweich, a Washington University law professor and former Ambassador for counter-narcotics and justice reform in Afghanistan, for having donated $500 in 2001 to Democrat Claire McCaskill when she was running for an easy re-election as state Auditor. This was five years before McCaskill was elected as a U.S. Senator, defeating a Republican incumbent.

Now Schweich is hitting back, noting Blunt's early attack. "I am flattered that Roy Blunt is so concerned about me that he has launched a vintage Washington-style smear campaign against me before I have even decided whether to run," Schweich said in a statement. "It underscores the need for our party to go in a new direction in this Senate race, demonstrates how vulnerable Blunt is feeling in light of the recent polls showing him being handily defeated by Robin Carnahan, and makes me more likely to run."