Sen. Ted Cruz (R-Tex.) talks with supporters at the annual Grassroots America We The People Champions of Freedom award dinner Sept. 23 in Tyler, Tex. (Andrew D. Brosig/Tyler Morning Telegraph via AP)

When Sen. Ted Cruz (R-Tex.) capitulated last Friday and announced his intention to vote for Donald Trump, it marked a key shift in the presidential race. Cruz was the highest-profile holdout from the Trump train, having weathered boos and scorn at the Republican convention in defense of his ideals. But the shift that was marked was more broadly was that Cruz was simply part of a wave. Other Republican holdouts have come on board — and that's a large part of why the race has gotten so close.

In the most recent Washington Post-ABC News poll, Trump now gets more support from those who backed someone else in the Republican primary than Hillary Clinton gets from voters who backed Sen. Bernie Sanders (Vt.) in the primary. That wasn't the case in The Post-ABC poll released earlier this month. At that point, fewer than two-thirds of registered voters who backed someone besides Trump in the primary planned to vote for him in the general. Now, that figure is 72 percent. About two-thirds of Sanders backers earlier this month planned to vote for Clinton — a number that has fallen to 61 percent.

(The Washington Post)

That aside, new polls released Monday in the shadow of the first presidential debate show a similar shift: more support for Trump in general and more support from Republicans. We tracked the past three polls from Monmouth and Quinnipiac Universities as well as our own to show that link.

(The Washington Post)

There's a correlation between the margin by which Clinton got more support from her party and the size of her lead over Trump in most of these polls. When Democrats were much more likely to back Clinton than Republicans were Trump, her leads were generally much bigger. Now that the gap between parties has narrowed, so has the margin.

(The Washington Post)

Remember: This was a conscious strategy by Clinton, made obvious at the Democratic convention. She portrayed Trump as an outlier in belief and in his political values, someone that wasn't representing the party well. It seemed to work, particularly when Trump then kicked off the post-convention period by getting into a fight with the parents of a dead soldier. But Clinton's lead faded over the course of August and September, as holdouts, including a certain senator from Texas, decided to get on board with their party's candidate.

At Monday's debate, Clinton will probably continue to try to peel Trump away from the Republican base, as she did before. But her best shot at creating that wedge may have passed.