Before the U.S. embarked on a possible diplomatic solution to the situation in Syria, a to use military force looked headed for defeat in the House. A showed a majority of members trending toward "no" over the last few days. No significant bloc of "yes" votes ever emerged.
Here's one reason why: There is no set of congressional districts whose voters back the strikes - voters in swing/marginal districts oppose it; as did voters in heavily Republican ones, and heavily Democratic districts opposed it even more so, which adds pressure on Democratic House members who might otherwise back President Obama. So there seemed no political gain at the moment for any House member from anywhere to back the strikes.
This chart breaks down voters' responses to
Swing districts here are classified as having voters with between +5 Republican and +5 Democratic average partisanship, Highly Republican districts have greater than +5 Republican tilt and Democratic ones, +5 or more towards Democrats.
Moreover, voters placing importance on the vote is also spread across district types: Voters in swing districts say this vote will matter, and so do voters in heavily partisan districts. Voters nationwide said their individual member's stance would matter at least a lot (more than four in 10 said so) or somewhat (another third.)
There of course is not enough sample in any one or two individual districts to gauge how any single member's constituents stand, so that may vary here and there, but this gives a broad picture of how the opposition prior to the president's speech was rather uniformly spread across all types of districts.