Dick Durbin and Al Salvi each wants to paint the other as an extremist candidate. Is this just mudslinging? It all depends on how you define the term.
In one sense an extremist is a wacko--somebody who accuses opponents of disrupting his daughter's wedding or raves about black UN helicopters. Salvi and Durbin are not extreme by this standard.
In another sense an extremist is anyone you disagree with about practically everything. Durbin and Salvi are so far apart on most issues that each may really believe the other is extreme. By this definition both men qualify.
A little more objective may be the definition of an extremist as someone who's far from the center. But what center, and how far? One reasonable yardstick is a comparison of each candidate's record with his party's centerline. Most political observers agree that legislatures have tended to polarize in recent years and have fewer moderate Democrats and Republicans, so even by this standard it may be more difficult than in the past to appear extreme. Durbin and Salvi have served in different legislative bodies, so we can't compare their votes on the same bills. But both have been rated by lobby groups of all persuasions. Does either of them vote consistently to the left or the right of his party's centerline? The short and surprising answer: in 1995 Durbin voted left of the Democratic average in eight ratings out of eight. Salvi voted right of the Republican average only three times out of eight.
Voting records don't tell everything. They can only show issues that came to a vote. They focus on some issues and not others. And they tell nothing about how a candidate works with colleagues behind the scenes in the legislature. But these ratings do suggest that in 1995 Durbin voted a bit more consistently liberal than Salvi voted consistently conservative.