And it's making lower-chamber Republicans both worried that their House conference won't have the padding needed if Hillary Clinton leads Democrats to the polls in droves in 2016 and bitter that they're punished for last cycle's success while the Senate, as one House GOP strategist put it, had "fumbled" its two prior opportunities for a majority.
"[The Senate GOP] has had some golden opportunities that we've blown, and as a result all the attention has been focused on the Senate—to the detriment of the House," said one consultant with a history of working House races, who, like many who talked for this story, requested anonymity to speak candidly.
Added another: "In the House, it's like there is no reward for success. And that's just the reality you live with."
The degree to which House outside groups are outgunned this cycle was evident last week, when the American Action Network and Congressional Leadership Fund announced they would spend $8 million on TV and digital ads and polling during the final two months of the campaign. By comparison, the main vehicle for outside spending by Democrats, the House Majority PAC, has already spent or plans to spend more than $22 million on TV ads alone.
Other groups have and plan to spend additional money on House races, including American Crossroads, the Chamber of Commerce, and Americans for Prosperity. But ad buys from national behemoths like the chamber have been isolated, and all of them have invested far more heavily on the Senate. Other groups aren't in a position to pick up their slack either.
What that's meant is the Democratic Congressional Campaign Committee has outraised the National Republican Congressional Committee, $136 million to $109 million, thanks in large part to the party's small-dollar-donor machine.
Certainly, the House GOP isn't bracing for losses on Election Day. A right-leaning map and favorable political environment ensure the party will pick up at least a few seats for 2015. But the cash disadvantage means they could have won more.
"If you're not outspending the other side, you're probably leaving some races on the table "¦ that if you really made an all-out push, you could probably pick up," said Andy Sere, a House GOP strategist.
It's not just the money either that's holding the GOP back. With cash on hand, Democratic groups like HMP have been able to reserve their ad time far in advance—a major tactical advantage as it, the DCCC, and Democratic campaigns themselves try to align their spending without legally coordinating with one another.
"It is frustrating because the House Majority PAC reserved their TV so early," said one House GOP strategist. "And so the DCCC had a clear sense of when they were going up and where they were going up. So it's literally like a symphony. The DCCC goes down, and the next day the HMP goes up. On our side, it's last-minute, and there's no sort of road map for anyone to follow."