It's going to be up to the voters in 2010 to decide how they view Democratic centrist congressmen, and both Democrats and Republicans are pushing hard to make sure that voter understands the nature of the ... ahem ... beast.

Blue Dogs are 51 House of Representatives Democrats, moderates who consider themselves more fiscally conservative than party leaders. But most also have voted for recent Democratic-authored budgets that increase spending well above the rate of inflation.

As a result, Republicans are taking aim, and starting Wednesday plan to run ads against moderates they see as vulnerable. A sample of the one planned against Arkansas' Marion Berry, a congressman since 1997:

"In Arkansas," the announcer says, "Marion Berry calls himself a BLUE DOG. A Blue Dog DEMOCRAT, that is. Berry claims he’s conservative on budgets and spending ... but this year in Washington, Marion Berry’s not voting like a Blue Dog ... He’s voting like a Lap Dog."

It goes on to tie Berry to President Barack Obama and House Speaker Nancy Pelosi. Blue Dogs have countered that they helped get spending levels down from what Obama sought - they did help get some cuts in the budget resolution approved recently - and their numbers alone give them enough clout to make members of both parties think hard before spending excessively.

The Blue Dog coalition has 51 members. Democrats control 256 House seats and 218 constitute a majority.