From September 25 to October 1, Donald Trump spent more than eight times as much on television and radio advertising as he did during the prior week, according to newly released from the Associated Press. Trump also widened the map and adopted a more offensive posture, adding five left-leaning states—Colorado, New Hampshire, Nevada, Iowa, and Maine—to the four states where he was already running ads (Florida, Ohio, North Carolina, and Pennsylvania).
During the prior week (September 18 to 24), Trump was outspent by Hillary Clinton by a tally of $19.5 million to $516,000 (according to A.P.'s slightly updated figures for that week). Rounding to the nearest whole number, that's a ratio of 38-to-1. In the most recent week (September 25 to October 1), Trump cut that ratio to just 4-to-1. Clinton's ad spending remained essentially constant over the two weeks, dipping slightly from $19.5 million to $19.4 million, while Trump's rose dramatically, from $516,000 to $4.4 million.
As I on Monday, there has been a strong correlation between Trump's ad spending and his success in the polls. While Clinton's ad spending has followed a pretty consistent pattern, Trump's has Overall, Clinton has outspent Trump by a ratio of 7-to-1 over the past three months. (It was 8-to-1 before the most recent week.) But during the three (consecutive) weeks when Trump improved on that ratio (in late August and early September), he closed Clinton's lead from 6.3 points to just 1 point in the Real Clear Politics average of recent polls. Trump's ad spending fell off greatly in the two weeks to follow, however, before rebounding in this most recent week.
During the most recent week, Trump made a particular strong push in Colorado. He actually outspent Clinton there, by a tally of $247,000 to $133,000. He also had a relatively strong presence in New Hampshire, where Clinton outspent him by a ratio of just 2-to-1 (again, rounding to the nearest whole number), and in Florida, where she outspent him by a ratio of 3-to-1. In addition, Trump outspent Clinton ($30,000 to $0) in Maine.
Trump has his most likely paths to victory. Moreover, if Trump still decides to make a strong push in Virginia or Michigan, then Clinton's failure to run ads there—while she has continued to run ads in Arizona, where she isn't going to win and doesn't need to win—means that he wouldn't have to overcome a recent ad deficit in either of those two states.
The real question is whether this most recent week marks the start of a Trump ad push that will extend through Election Day, or whether it's a 1-time blip. Since Clinton has enjoyed a 7-to-1 advantage in ad spending (on average) across the past 13 weeks, anything significantly inside of that ratio will likely provide a boost for Trump and cause a problem for Clinton.