Updated 1:33 p.m.

The Democratic Congressional Campaign Committee dropped nearly $6.6 million in new independent expenditures this week, according to reports filed Tuesday with the Federal Election Commission, as the party faces an expanding landscape of vulnerable incumbents.

In the Mid-Atlantic region, the Midwest and the Southwest, the DCCC spent to help incumbents who increasingly appear to be in jeopardy. The committee has now spent just less than $19 million toward the $52 million strategists expect to dole out before Election Day.

The committee’s spending, however, could be dwarfed by the influx of outside spending by Republican groups. American Crossroads and the affiliated Crossroads GPS have already raised $56 million so far and have increased their fundraising goal to $65 million. The Hotline first reported the group’s new fundraising figures.

Meanwhile, the Wall Street Journal reported Wednesday that an “alliance of Republican groups is launching a $50 million advertising blitz this week in a final push to help the GOP win a majority in the House, representing the biggest spending blitz ever by such groups in a congressional election campaign.”

The alliance includes the American Crossroads and Crossroads GPS, founded by Karl Rove; American Action Network, led by former Sen. Norm Coleman (R-Minn.); and the Commission on Hope, Growth and Opportunity.

“There’s an effort to be communicating with each other to make sure no one is stepping on each other’s efforts,” Jonathan Collegio, communications director for American Crossroads and Crossroads GPS, said Wednesday. “Many of the groups talk on the phone at least once a week.”

Collegio added that there is no coordination with the party committees, per FEC regulations.

The outside groups are assisting GOP challengers, most of whom are at fundraising disadvantages against well-funded Democratic incumbents. The Democrats are receiving extra help from the DCCC as well, which through the end of August had a cash-on-hand advantage of more than $13 million over the National Republican Congressional Committee.

Democrats on Capitol Hill have called for an IRS investigation into the funding of outside groups like American Crossroads and Crossroads GPS.

“Following the Citizens United ruling — where corporations trying to influence public policy or foreign money could be used to influence American elections — voters deserve to know who is behind these ads and what their motivation is,” DCCC spokesman Ryan Rudominer said. “Now more than ever, voters have a reason to be skeptical of these shady pro-outsourcing right wing groups that refuse to disclose who is funding them.”

The NRCC has so far spent just less than $20 million in IEs.

This week the DCCC reported spending another $355,000 on behalf of Rep. Frank Kratovil (D-Md.), whose 1st district has now received a total of $803,000 in committee spending. The district is also seeing spending by the NRCC and the alliance of outside GOP groups.

Other Democrats receiving sizable boosts in the DCCC’s latest spending include Reps. John Salazar (Colo.), Phil Hare (Ill.), Harry Mitchell (Ariz.), Ann Kirkpatrick (Ariz.), Dina Titus (Nev.) and Baron Hill (Ind.).

The increased spending comes at the same time the committee is decreasing spending in other districts, most of which they appear unlikely to hold. The committee has now completely cut off spending in three open-seat races in which it had reserved time: Tennessee’s 8th district, Indiana’s 8th district and Kansas’ 3rd district.

Incumbents in districts that have been cut off include Democratic Reps. Steve Driehaus in Ohio’s 1st district, Suzanne Kosmas in Florida’s 24th district and Kathy Dahlkemper in Pennsylvania’s 3rd district.