Take the 6th Congressional District of Massachusetts, for example. The DCCC has allocated about $1.4 million to help Rep. John Tierney hang onto that seat. The nine-term congressman, whose district is located northeast of Boston, has been dogged by ethics issues; he narrowly won re-election in 2012 with 48.3 percent of the vote in a three-way race. It's a Democratic-oriented district, but more politically marginal than the typical Massachusetts district. Democrats are also spending in California's 26th Congressional District, represented by first-term Rep. Julia Brownley. The DCCC has allocated $950,000 for cable TV campaign ads on Brownley's behalf from late September to Election Day. Brownley beat her Republican rival by just 5.4 percentage points, but ran behind Obama's winning performance there. That has emboldened Republicans who see her seat as a potential pickup, despite the Democratic voter registration edge.