But the analysis provides a broad assessment of the relative financial strength of the two parties in what is expected to become the first midterm election to surpass $5 billion in total spending. And it hints at how the two sides might allocate their resources as Democrats try to capitalize on their energized base to claw control of the House away from Republicans and make inroads on the state level and, less likely, in the Senate.

The Republican cash advantage could allow the party to bolster financially strapped campaigns that still have a chance, and fund an emerging strategy of nationalizing the race around President Trump and culturally divisive issues like immigration and the confirmation of Justice Brett M. Kavanaugh. Republicans are issuing ominous warnings about liberal “mobs” deploying dirty tactics to help Democrats smear conservatives and push the country toward socialism.

“We’re seeing parity in the money race, and I expect both sides to be taking a pretty hard look at their races in the next week or two, so that they can cut some, and double or triple up on others,” said Michael J. Malbin, the executive director of the Campaign Finance Institute, a nonpartisan think tank that analyzes campaign fund-raising and spending.

The bigger strategic issue for candidates, party committees and super PACs, he suggested, will be how they adjust to Mr. Trump’s efforts to nationalize the midterm elections in a manner that defies recent political norms.

“President Trump in the last two weeks has managed to dominate free media coverage in a way that is firing up his base, and the value of that cannot be measured in the same way you measure super PAC advertising or party committee spending,” he said.

On the Democratic side, a pair of top super PACs — Priorities USA Action and the League of Conservation Voters’ PAC, known as the LCV Victory Fund — last week launched a joint $300,000 digital get-out-the-vote advertising campaign. The ad, which is intended to mobilize young voters and voters of color in four competitive House districts, seemed to suggest that a vote for Republicans is a vote for white nationalism.